One way of solving systems of linear equations is by adding a multiple of one equation to the other. the multiplier for one equation is chosen so that one of the two variables will cancel out in the sum. what should you multiply the equation y=0 by so that when added to x+y=40 the variable y will cancel out?

We want to use elimination to solve
y = 0                     (1)
x + y = 40             (2)

Multiply (1) by -1 to eliminate y.
-y = 0                    (3)

Add (2) and (3).
x + y + (-y) = 40 + 0
x = 40

Multiply by -1.

The question is kind of confusing. if it's asking how many variations of answers can you give. then do 4^5 for your answer.this would be something like the first question could be a and the 2nd c or first b next c etc. if you can, ask the teacher for a better confirmation of what it's asking. if i'm assuming correctly what it's asking, it's 625 different variations.