Question

1.5 gallons = x quarts

Answer 1

Given:
1.5 gallons = x quarts

1 gallon is equal to 4 quarts.  1 gal = 4 quarts

1.5 gallons * 4 quarts/gallon = 6 quarts.

There are 6 quarts in 1.5 gallons.

Answer 2

1.5 gallons = x quarts.      But 1 gallon = 4 quarts.

1.5 * 4 quarts = x quarts

6 quarts = x quarts.

x quarts = 6 quarts.       Compare both statements.

x = 6.