Answer:
5.325 gallons or
Step-by-step explanation:
According to the given problem, Dr. Silva's tank holds up to 16 7/8 gallons = 16.875.
Transform 7/8 into decimal: Divide the numerator by the denominator = 0.875. Add that to 16, and you'll have the full tank capacity of 16.875.
Next, the prompt states that she filled 11.55 gallons' worth of gas. To find how much her tank had before she filled it, you could simply subtract the full tank capacity and the amount of gass added into the tank.
16.875 - 11.55 = 5.325 gallons or (13/40 is the same as 0.325).