system of equations: x + y + 3z = 600, x + y + z = 400

[Love21]

x + y + 3z = 600
x + y + z = 400

In the system of equations above what is the value of x + y?
How would you go about determining x +y ?
obviously the 3 times z gets it from 400 to 600
what's the best way to solve
thanks!

 

[o_O]

Re: system of equations

Solve for z by subtracting both equations. Then, once you have the value of z, just plug it back into one of the equations and solve for (x + y)

 

[Deleted member 4993]

x + y + 3z = 600
x + y + z = 400

In the system of equations above what is the value of x + y?
How would you go about determining x +y ?
obviously the 3 times z gets it from 400 to 600
what's the best way to solve
thanks!

If multiply the second equation by 3 - and subtract the first equation from it - what do you get?