1. 7 gallons = 7 × 4 = 28 quarts
so, the ratio of 2 quarts to 28 quarts = 2 / 28 = 1 : 14

2. 5 dollars = 500 cents
so, the ratio of 500 cents to 25 cents = 500 / 25 = 20

3. Meters cannot be expressed in terms of kilograms, so this ratio cannot be expressd.