Use proportions.
(1/3)/6 = x/54
To find x, we first need to set the denominators for both fractions equal to each other. Multiplying 6 by 9 will give us 54 as the denominator for the first fraction. But by multiplying the denominator by 9, we are required to multiply the numerator by 9 as well; one of the rules of fractions.
9(1/3)/(6 * 9) = x/54
(9/3)/54 = x/54
3/54 = x/54
Multiplying both sides by 54 to get rid of the denominators, we will see that x is 3, which tells us that 3 inches represent 54 feet in the scaled drawing.