How to substitute equations for solutions

3x-2y=9
y=2x-7

First I would rewrite it so all the x's and y's are in the same places

3x-2y=9
-2x+y=-7

Then multiply the bottom one by 2
-4x+2y=-14

Then add the equations
   3x-2y=9
+-4x+2y=-14

-x=-5 or x=5

The substitute this into one of the original equations to solve for y.

y=2(5)-7
y=3

So your answer is x=5 and y=3 or (5,3)

Hope this helps.

What is your question?

Maybe the answer is 20mm. all i really did was just multiply, which is obvious.