Mia buys 3 gallons of gas that costs d dollars per gallon. Bob buys g gallons of gas that costs $3 per gallon. a. Write an expression for the amount Mia pays for gas.
3d. Its as simple as that. Since you have to multiply the 3 gallons by the price of the gas, or d, you can put 3d or 3 gallons multiplied by dollars per gallon.
The answer will be 3d