Question

Jill wants to solve the following system using the elimination method:

y = x + 8
y = 3x − 11

What number should the equation y = x + 8 be multiplied by to eliminate x?
−1
−2
−3
3

Answer 1

-3 as in the first equation x = 1x so multiply it by -3 you’ll get -3x.

Answer 2

-3

Explanation:

To use the elimination method, we need the variable we want to eliminate to have the same coefficient number in both equations, but with the opposite sign. Thus, when adding the equations that variable will be eliminated.

The variable x in the first equation is the following:

x

and the x in the second equation is:

3x

So we must multiply the first equation by -3, so it becomes:

-3y = -3x + 8

and we can see that now, the x's in both equation have the same coefficient number but a different sign (one positive and one negative) which is what we need to apply the elimination method.