On a long road trip, a family used 12 gallons of gas. at the end of the trip, there were 3 gallons left in the tank. how many gallons of gas were in the tank at the start of the trip?

The amount of gas used and the amount of gas left are illustrations of arithmetic operations.

15 gallons were in the tank at the start of the trip

The given parameters are:

The required equation is:

Substitute known values

Evaluate like terms

Hence, 15 gallons were in the tank at the start of the trip

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