what would the equation be? How much would one gallon cost?

Question

You buy 7 gallons of gasoline at p dollars per gallon and pay $26.88. Write and equation to find the price of one gallon of gasoline. Then find the price of one gallon of gasoline.

Answer 1

In your first sentence, 7p = 26.88 is implied.  Now, AN equation to find the price of one gallon--simply solve for p = 26.88/7; p = $3.84 per gallon.