The net force exerted on an object is the sum of all vector forces applied to it. If no acceleration is achieved, the net force is zero.
We have three forces applied to the cylindrical weight: Its own weight and the two components of the tension of each rope. Knowing they form an angle with the vertical, then each component is given by
The sum of all forces in the vertical direction is
Well first you have to divide 620/20 which is 31. So his car goes 31 miles per gallon so you have 2 gallons and .25 of a gallon. So first off 2*31=62 miles then the 1/4 or .25. Multiply the 31 by .25 which is 7.75 now add 62 and 7.75 and you get how far his car can go.