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

7 cubic yard

Step-by-step explanation:

Let the compost purchased be x cubic yard

And the topsoil purchased be y cubic yard

Hence

x+y=10 (A)

Also

Cost incurred in buying compost at a rate of $25 per cubic yards = 25x

Cost incurred in buying topsoil at a rate of $15 per cubic yards = 15y

Total cost incurred = 25x+15y=180

Diving whole equation by 5 we get

5x+3y=36 (B)

Multiply A by 3 and subtract it from B

5x+3y=36

- - -

3x+3y=30

2x=6

x=3

Putting this value in A

x+y=10

3+y=10

y=10-3=7

Hence she purchased 7 cubic yards of topsoil.

5050 i think

step-by-step explanation: