3x-2y=-7. Y=x+4

Question

Use substitution to solve the system of equations 

Answer 1

3x-2y=-7  y=x+4

To substitute, replace "y" in the first equation with x+4 since y=x+4. So now you have:

3x - 2(x+4)= -7

  Now use distribution and solve for x:

3x - 2x - 8= -7

x - 8= -7

x= 8-7

x=1

Now substitute your value of x back into the equation to get your y value.

Answer 2

Substitution is substituting one thing for another.

 

Here you have:  y = x+4

"y" is x+4

 

so you can substitute x+4 for y in the other equation. This combines the two equations and it becomes a one variable, x equation you can then solve.

 

3x - 2y = -7

 

becomes..

 

3x - 2(x+4) = -7

 

3x - 2x - 8 = -7

 

x - 8 = -7

 

x = -7 + 8

 

x = 1

 

then use this (x = 1)  in either of the original equations to solve for y