Simple substitution question

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kmomma1999

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The problem I am working on is kind of lengthy so sorry about all of the reading. The first part of the question is : The sales representative informs you that there are two floor plans still available, and that there are a total of 56 houses available. Use x to represent floor plan #1 and y to represent floor plan #2. Write an equation that illustrates the situation.
To this question I answered: x+y=56
The second part is: The sales representative later indicates that there are 3 times as many homes available with the second floor plan than the first. Write an equation that illustrates this situation. Use the same variables you used in part a.
To this I answered: x+3y=56
The third part is the part I have the question about but I thought it would be easier to understand me if I gave you all of the information.
Use the equations from part a and b of this exercise as a system of equations. Use substitution to determine how many of each type of floor plan is available. Describe the steps you used to solve the problem.
My question to this is I know that I am using substitution, but since this is the first time I have used it, does this mean that I just use any number to replace "y" in the equation that I gave in the second part of the question?
If I do pick just any number as a substitution for "y" then how will I get the same answer or the right answer as someone else if they substituted with another number?
Thanks!!
 
In this problem... they are not asking you to arrive at one equation, then edit it.

They are asking you to get x+y=56 then to get another equation for the 2nd situation. From there you go on with your substitution. If you do not know how to do that let me know and i shall assist you further.
 
Sorry if my question was not worded properly. That is what I am asking though. Basically how to do the substitution. Am I right in saying that I need to just pick a number to replace y in the second equation: x+3y=56 ??
 
kmomma1999 said:
The problem I am working on is kind of lengthy so sorry about all of the reading. The first part of the question is : The sales representative informs you that there are two floor plans still available, and that there are a total of 56 houses available. Use x to represent floor plan #1 and y to represent floor plan #2. Write an equation that illustrates the situation.
To this question I answered: x+y=56 <<< correct but you need to define 'x' and 'y' .......................(1)
The second part is: The sales representative later indicates that there are 3 times as many homes available with the second floor plan than the first. Write an equation that illustrates this situation. Use the same variables you used in part a.
To this I answered: x+3y=56<<< This is not correct

According to your first problem

x = # of houses of first floor plan

y = # of houses of second floor plan

Now for the second problem - we keep same nomenclature - but extra information comes in:
there are 3 times as many homes available with the second floor plan than the first

that is

y = 3x ( however first equation is still valid.).....................................(2)
The third part is the part I have the question about but I thought it would be easier to understand me if I gave you all of the information.
Use the equations from part a and b of this exercise as a system of equations. Use substitution

Use information from (2) into (1) - substitute 'y' - and solve for 'x'.

to determine how many of each type of floor plan is available. Describe the steps you used to solve the problem.
My question to this is I know that I am using substitution, but since this is the first time I have used it, does this mean that I just use any number to replace "y" in the equation that I gave in the second part of the question?
If I do pick just any number as a substitution for "y" then how will I get the same answer or the right answer as someone else if they substituted with another number?
Thanks!!
Click to expand...
 
Ok so you are saying that my first equation is correct as x + y = 56. The second equation should be y=3x (which does make sense now). But my question now is do I substitute in the second equation or do I put the the second equation into the first and solve that way?
 
kmomma1999 said:
Ok so you are saying that my first equation is correct as x + y = 56. The second equation should be y=3x (which does make sense now). But my question now is

do I substitute in the second equation or do I put the the second equation into the first and solve that way?

the second equation gives you

y = 3x

Use this information to substitute y - in the first equation.
Click to expand...
 
Thank you so much!! As soon as I read this last post, it clicked. THis is my last week of this class and even though I am doing well, Substitution and elimination are the two things that I am having trouble with. I am sure I will post one on elimination in a few minutes!! Thank you again for your help. I sometimes think that those of you who help out on here do not get the Thanks that you deserve!!
 
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