I was just in the same situation, you got this. the answer is A.
Firstly, let's create a function of f(t) where t represents the time that has past, and f(t) represents the amount of rainwater. We know that when t=1, then f(t)=10, and t=2 then f(t)=15. So, let's take that and analyze it:
(1,10)
(2,15)
m = (15-10)/(2-1) = 5
y-intercept = 5
∴ f(t) = 5t+5
Now we just evaluate t for 10:
f(10) = (5*10)+5
f(10) = 55
Whole
so think of it as a interger
Yes, the 36" shelf can hold all 24 books. As 5/4=1.25" meaning, you take 1.25X24=30". So 24 books only take up 30 inches of a 36 inch shelf.