Let x = number of miles.
Price of Sam's Vans: 2 + 0.5x
Price of Rock Rides: 1 + 0.75x
Set the prices equal to each other, and solve for x, the number of miles.
2 + 0.5x = 1 + 0.75x
-0.25x = -1
x = 4
Answer: The two prices are equal when he travels 4 miles.