If Habib 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?

Question: If Habib 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?

Solution:
Let full capacity = C gallons.
According to the question,
(3/4)C + 5 = (7/8)C
⇒ (7/8 - 3/4)C = 5
⇒ {(7- 6)/8}C = 5
⇒ (1/8)C = 5
⇒ C = 5 × 8
∴ C = 40
So the full capacity will need 40 gallons