Question 1157494
Let the quantity of old fuel be x
Quantity of new fuel be y 

since total capacity of the tank is 56 
=> x + y = 56   ..... (1)

Also , total cost of fuel

= 4x + 7.36y = 328.16  ....(2)

Multiplying equation (1) with 4 we get,
  4x + 4y = 224  --------- (3)

Subtracting equation 3 from equation 2 we get,

3.36 y = 104.16 
therefore y= 104.16/3.36 = 31

therefore new fuel is 31 gallon.
Old fuel = 56 - 31 = 25 gallon

Ans: 31 gallons of new fuel were required to fill the tank.