If Henry were to add 5 gallons of water to a tank that is already 3/4 full of water, the tank would be 7/8 full. How many gallons of water would the tank hold if it were full?  Choose the correct choice from the following:
A) 25
B) 40
C) 64
D) 80
E) 96

Rationale: 7 / 8 x - 3 / 4 x = 5 galls 1 / 8 * x = 5 gallons x = 40 gallons answer : b
Answer: B