The answer to your question is -36
Here are the unit rates involved:
$7.68 / 1 case = $7.68 per case
$7.68 / 24 cans = $0.32 per can
1 case / $7.68 = 0.13 case per $
24 cans / $7.68 = 3.125 cans per $
And of course ...
24 cans / 1 case = 24 cans per case
1 case / 24 cans = 0.041666... case per can
Add y to both sides in 1st equation
-2x=y
sub -2x for y in2nd equation
3x-(-2x)=10
3x+2x=10
5x=10
divide 5
x=2
sub back
-2x=y
-2(2)=y
-4=y
(x,y)
(2,-4)
C is ans
