Answer: 12.73 feet
Step-by-step explanation: We aren't told the type of vessel. I'll assume a cylindrical tank.
Volume of a cylindrical tank is V = πr²h
I'm assuming the 1210 is in units of volume, such as ft^3
1210ft^3 = πr²h
h = (1210ft^3 )/(π(5.5)²)
h = 12.73 ft