Which one will it be?

In a two-digit number the units' digit is 7 more than the tens' digit. the number with digits reversed is three times as large as the sum of the original number and the two digits. find the number.

At store a, erasers are sold individually. the cost y of x erasers is represented by the equation y=0.75x. the costs of erasers at store b are shown in the graph.

Your car's gasoline tank holds 18 gallons of gasoline. on a trip in canada, the tank is one-quarter full. you want to fill the tank. how many liters of gasoline are needed to fill the tank