Answer: The required number of gallons of gas is 4.
Step-by-step explanation: Given that Hanks pickup can travel 85 miles on 5 gallons of gas.
We are to find the number of gallons of gas needed to travel 68 miles.
We will be using the UNITARY method to solve the given problem.
Number of gallons of gas needed to ravel 85 miles = 5.
So, number of gallons of gas needed to travel 1 mile will be

Therefore, the number of gallons of gas needed to travel 68 miles is given by

Thus, the required number of gallons of gas is 4.