Need help with these 3

1.) x = 110

So for 3 to become 15 it would have to be multiplied by 5 because 3 x 5 = 15. And if I multiply the numerator by anything I always have to do the same to the denominator. So I multiply 22 x 5 = x. x = 110

2.) x = 72

For 16 to become 2 it has to be divided by 8 because 16 ÷ 8 = 2. And I have to do the same to the numerator of course, so i have to find x ÷ 8 = 9. I know the answer by memory, but for some it's easier to rewrite this as 9 × 8 = x. x=72

3.) c = 24

For 5 to become 40 it must be multiplied by 8 because 5 × 8 = 40. I have to multiply 8 by the numerator as well and 3 × 8 = 24. c = 24

i assume that by 5 you mean 5 gallons.

(20)(0.25) = 15

removing 15 gallons reduces the tank from 20 to 5.