Question

How do you solve substitution problems in Pre Algebra

Answer 1

Get x or y alone in one equation and plug it in for the next. Then save for x/y and plug your answer in to either equation to get the other variable...For Example: 2x+8y=-8 and 4x=-64
4x=-64y
Divide by 4 on each side and get x=-8y
Plug in -8y for x in the other equation and solve for y
2(-8y)+8y=-8
-16y+8y=-8
-8y=-8
y=1
Plug in y to original equation 2x+8y=-8 to find x
2x+8(1)=-8
2x+8=-8
Subtract 8 and get 2x=-16
And solve for x so x=-8
Coordinates: (-8,1)

Answer 2

You multiply both of the equations until you have two of the same term the same like for example, say I have 4x and 5x. You want to multiply until both have the same number, so multiply 5x by four, then multiply 4x by five, and you will get 20x, then both of those cancel out and you will be left with the other variable, and you just solve like a normal equation.