To find the vehicle's consumption rate in miles per gallon (mpg), you divide the number of miles driven by the number of gallons used.
Given:
- Miles driven = 90 miles
- Gallons used = 4 gallons
Calculation: \[ \text{Miles per gallon} = \frac{\text{Miles driven}}{\text{Gallons used}} = \frac{90 \text{ miles}}{4 \text{ gallons}} = 22.5 \text{ miles per gallon} \]
So, the correct response is: 22.5 miles per gallon.