Question 710728
{{{(240miles)/(("20.0 miles" / "1 gallon"))=(240 miles)*(1 gallon / "20 miles")}}} gives you the number of gallons of gasoline used.
Multiplying times the cost per gallon of gasoline, you get the cost of the gasoline for the trip:
${{{(240 miles)*(1 gallon / "20 miles")(2.50/ "1 gallon")}}}= ${{{240*2.5/20}}}= ${{{highlight(30)}}}