Solving For The Unknown

[LittleBookWorm]

Hello, I'm new on here. I am homeschooled and I am in 9th grade. I'd like some help please, with solving for the unknown. I can do an equation like 2D=8, but I'm struggling with the more complicated ones. For example, I get stuck on a problem like this:

l-1-3x4l= 3D-8+7-D
(Just so you know, the lines on either side of the -1 and the 4 are intended to be bars, not letters or numbers.)

I try to solve the problem, but I'm not sure that I do it in the right order:

l-4x4l=3D-15-D
l16l=3D-15-D

Then when I finish that, I can't figure out the rest, and I'm not even sure that I did that part right. I'm having a really hard time with this concept, and the curriculum I use, Math U See, doesn't really tell you why the numbers and letters get switched, why they get placed where they do, or explain how you get the answer. Please help me understand this concept, because it's only getting harder!!! :???:

Thank you in advance for any help!

 

[rbcc]

l-1-3x4l= 3D-8+7-D

so just for clarification the

3x4 is 3 times 4 right? the x is not a variable?

the bars mean absolute value, so the final answer within them will be positive. Ok so lets start with the left side

l-1-3x4l

3(4)= 12

|-1-12|= |-13| the absolute value signs mean that the left side is positive 13

now for the right side

3D-8+7-D

lets group like terms

3D-D-8+7

then simplify

2D-1

so putting the left and right side together we have

13=2D-1

and you can take it from there right?

*note use BEDMAS to figure out what to do first

B= brakes
E= exponents
D= division
M= multiplication
A= addition
S= substitution

 

[LittleBookWorm]

Yes, the x was a multiplication sign, not a variable. Sorry about that.

Thank you very much for responding so quickly and thoroughly! Thank you also for the BEDMAS tip! That should help me in the future.
OK, so here is the problem solved from where you left off:

13=2D-1
13+1=2D
14=2D
D=7

I really apprecitate the time you took to help me, rbcc. I'm really glad I found this message board and I am sure I'll be back!

 

[rbcc]

no problem your answer is correct!

for the BEDMAS thing, the S should be subtraction

 

[coughsyrup78]

Bedmas/pemdas

Just curious, is BEDMAS the same as PEMDAS? Is it different in different countries or something?

 

[willmoore21]

We used to have BODMAS,

where O was pOwers.

Maybe they thought the word exponent was too difficult.