the first thing you want to do is convert the 1/2 beside the 12 to 2/4ths so you can subtract the two fractions. your new equation would be 12 2/4 - 9 1/4. subtract 1/4th from 2/4ths and you'll get 1/4th. subtract 9 from 12 and you'll get 3. your answer comes up as 3 and 1/4th.
