Answer
Hector should expect to get 28.32 miles per gallon.
Work Step by Step
We can use the following guideline to solve this problem,
Current gas mileage + Increase = New gas mileage
So, 24 + 18% $\times$ 24 = New gas mileage
24 + .18 $\times$ 24 = New gas mileage
24 + 4.32 = New gas mileage
28.32 = New gas mileage
Hector should expect to get 28.32 miles per gallon.