How do you solve this system of equations using the substitution method x- y = 4 and 6x + 4y = - 66?

1 Answer
Oct 19, 2017

y=-9, x=-5

Explanation:

x-y=4 rArr equation 1
6x+4y=-66 rArr equation 2

Make either x or y the subject of equation 1, so you can substitute the values of in into equation 2.

x=4+y

Substitute this into equation 2.

6(4+y)+4y=-66
24+6y+4y=-66
10y=-90
:.y=-9

To find x, substitute y=-9 back into either equation 1 or 2.

x-(-9)=4
x=4-9
:.x=-5