Question

Use the substitution method to solve the system of equations.
x+y=11
-x=-y-9

Answer 1

Like you said, we need to use substitution to solve for y.

`x + y = 11\\-1(-x = -y - 9)\\\\x + y = 11\\x = y + 9\\\\y + 9 + y = 11\\\\2y + 9 = 11\\\\2y = 20\\\\y = 10`

Now that we've solved for y, we can plug in the number we got into one of the original equations. (You can choose either equation, but I will use the first one.)

`x + 10 = 11\\\\x = 1`

Now we have the solution of this system.

`(1, 10)`