28% of what number is 3 1/2 ?

Is 12.50 the answer?

3 1 / 2 = 6 / 2 + 1 / 2 = 7 / 2

28 % = 28 / 100

( 7 / 2 ) / ( 28 / 100 ) =

( 7 * 100 ) / ( 2 * 28 ) =

700 / 56 = 12.5

OR

3 1 / 2 = 3.5

28 % = 28 / 100 = 0.28

3.5 / 0.28 = 12.5