B wouldn't work because it would be safe to assume that it represents the quintuple of the sum. C also wouldn't work because although the y is tripled, the 2 isn't. And D wouldn't work because it is only tripling 2.
A should be your answer since you are distributing the number 3 which is the same thing as a triple to get the sum of the answer which is 3y + 6.
3/45 = 20/x...3 in to 45 seconds = 20 in to x seconds cross multiply (3)(x) = (45)(20) 3x = 900 x = 900/3 x = 300...300 seconds (or 5 minutes)to fill the tub with 20 inches
