Helena uses a mixture of compost and topsoil in her garden. She purchased a total of 10 cubic yards of compost and topsoil for $180. If compost costs $25 per cubic yard and topsoil costs $15 per cubic yard, how many cubic yards of topsoil did she purchase?
A. 3
B. 4.5
C.5.5
D. 7

Question

Narad · Answer

Let x= cubic yards of top soil
them, 10-x= cubic yards of compost
Then,
$$(10-x)*25+x*15=180$$
Solving this equation for x will give you the cubic yards  of top soil