Answer:
The tank can hold up to 9 gallons.
Quick Review:
By doing the inverse of 7/12, 12/7, when you multiply it, you'll get a value of 1.
7/12 * 12/7 = 1
Doing the Problem:
By multiplying 5 1/4 by 12/7, you'll get the answer. But first, convert 5 1/4 into an improper fraction.
5 1/4 ---> 21/4
Okay, lets go!
21/4 * 12/7 = 252/28
When reduced, this gives you the answer 9/1, or 9 gallons.
Hope that helps, :)