Answer:
120 gallons
Explanation:
For questions like this, it is convenient to determine a ratio with the number of minutes being 1. We know that gallons are proportional to minutes, so if we divide minutes by 3 (to get 1 minute), we also divide gallons by 3 (giving 12 gallons).
Similarly, we can multiply both gallons and minutes by the same value. Multiplying the above result by 10, we get 120 gallons in 10 minutes.
36 gal : 3 min
= 12 gal : 1 min . . . . . . divide above by 3
= 120 gal : 10 min . . . . multiply previous by 10