How is 1.5 quarts equal to 6 gallons?

Answer 1

It's not. Those numbers are backwards. 1.5 gallons is equal to 6 quarts.

1 gallon = 4 quarts

1.5 gallons = (1.5 x 4) = 6 quarts.

Answer 2

There seems to be a mistake in the conversion you provided. 1.5 quarts is equivalent to 0.375 gallons, not 6 gallons. To convert quarts to gallons, you would divide by 4 since there are 4 quarts in a gallon.