need help with word problem

Question

Jada walks up to a tank of water that can hold up to 10 gallons. When it is active, a drain empties water from the tank at a constant rate. When Jada first sees the tank it contains 7 gallons of water. Three minutes later the tank contains 5 gallons of water. 

A. at what rate is the amount of water in the tank changing? WE HAVE THIS ANSWER

 

B. How many more minutes will it take to drain completely?

C. How many minutes before Jada arrived was the water tank completely full?

Answer 1

A. (7 - 5)/3 = 2/3, so 2/3 gallon per minute.

 

B. 5/(2/3) = 5(3/2) = 15/2 = 7 1/2 mins

 

C. 3/(2/3) = 3(3/2) = 9/2 = 4 1/2 minutes