The answer would be C. 8.
I would cross multiple the fractions (3*40) and (15 * x)
That would equal 15x= 120
Divide both sides by 15 and you get 8
Or
You could say: what number times 3 gives me 15? The answer would be 5 and then you would divide 40 by 5 to get 8.
Hope the explanation helps :)
