Answer:
25 gallons
Step-by-step explanation:
Assuming miles-per-gallon is a constant, the amount of gas is proportional to the miles driven:
gallons/(500 mi) = (13 gal)/(260 mi)
gallons = (500 mi)/(260 mi)(13 gal) . . . . multiply by 500 mi
gallons = 25 gal . . . . do the arithmetic
The van will need 25 gallons of gas to go 500 miles.
