Final answer:
To calculate the amount of gas initially in the tank, divide the total money spent by Barb, 'd dollars', by the cost of gas per gallon, '$1.25 per gallon', to determine the gallons added. Then, subtract this from the tank's total capacity, which is 2 gallons.
Step-by-step explanation:
The question asks to find the amount of gas in gallons that was in Barb's motor scooter tank before she filled it. Since the gas costs $1.25 per gallon and Barb spends d dollars to fill up the tank, we can calculate the number of gallons she put in her tank by dividing the money spent, d dollars, by the cost per gallon, which is $1.25 per gallon.
To find the amount of gas that was in the tank before Barb filled it, we first need to know the tank's total capacity, which is 2 gallons. We then subtract the gallons she added from the total capacity. The number of gallons added is d divided by 1.25. So, the amount of gas previously in the tank is 2 - (d / 1.25) gallons.