Answer
Answer 7.5 Hours.
Work Step by Step
Let's assume the x is hours mover can run on 2 gallons of gas.
Now, we will write the proportion for the given details
$\frac{0.8}{3} = \frac{2}{x}$
so. $0.8\times x = 2\times3$ (cross multiply)
$0.8 x = 6$
$x = 7.5 $ (divide both sides by 0.8)
7.5 hours mover can run on 2 gallons of gas.