In the second one I'm pretty sure you just measure the length of the points.
2x - 3 = y
-3x + 5 = y
-4/5x -2 =y
1/2x + 9 = y
I can't see the graph but let's use logic
hmm, more than 10 cubic feet of topsoil so the first and 2nd options are wrong
let's ee the costs
3rd option
10*1=10
2*12=24
10+24=34 and 34<50, that is fine
4th option
3*10=30
2*12=24
30+24=54
54>50, nope, that is over cost
answer is 3rd one
the one with 1 cubic yard compost and 12 cubic yard topsoil
the answer to your question is 7