Final answer:
The expression 15n + 2(3p) represents the amount Isaiah spent buying gasoline and snacks. By substituting the values of n and p into the expression, we can calculate the total amount.
Step-by-step explanation:
The expression 15n + 2(3p) represents the amount Isaiah spent buying gasoline and snacks. In this expression, n represents the price of each gallon of gasoline and p represents the cost of each snack that he bought. To find the total amount Isaiah spent, we can substitute the values of n and p into the expression and simplify. For example, if the price of each gallon of gasoline is $2 and the cost of each snack is $1, the expression would become 15(2) + 2(3 * 1), which simplifies to 30 + 6 = 36.