In order to calculate what his salary is this year, you need to divide $3,600 / 12% since $3,600 equals 12%. $3,600 / .12 = $30,000. If his salary is $30,000 it was 3,000 less last year, or $27,000.
to divide fractions you take the reciprocal of the second fraction (switching the numerator and denominator) and multiply it so the equation turns into