3 3/5 gallons of gasoline would cost $4.50
This is because when you multiply 1.25 by 3 you get a product of 3.75.
Then, you multiple 1.25 with 3/5 and get a product of 0.75.
Add the two together, and you receive a sum of 4.50.
So, the cost for 3 3/5 gallon is $4.50.