McDougal Littell Algebra 2, Chapter 3, 3.2, Section 3.2, Problem 4

We have the equations: x+3y=-2 and -4x-5y=8 . We have to isolate one of the equations' variables in order to do the substitution method. In this case, let's isolate the x in the first equation.
Rewrite the equation.
x+3y=-2
Since it is addition next to the x, we have to do the opposite operation to isolate x. Subtract 3y on both sides to isolate x.
x+3y-3y=-2-3y
Simplify.
x=-2-3y
Now, plug in this equation into the 2nd equation we have to solve.
2nd equation before plug-in: -4x-5y=8
2nd equation after plug-in: -4(-2-3y)-5y=8
Distribute the -4.
8+12y-5y=8
Combine like terms.
7y=0
Divide 7 on both sides to isolate the y.
y=0
Now that you have found y, find x by plug in the solution of y into any the original equations.
x+3(0)=-2
Simplify
x=-2
CHECK: plug in the solution of x and y into both equations to see if you got the correct answer.
-2+3(0)=-2
-4(-2)-6(0)=8
Since we checked the answer, and the answer came out to be -2 and 8 in the first and second equation, respectively... x=-2, y=0