The common multiple of 12 and 20 is 60. You've got to multiply the first one by 5 and the second by 3. 5*5= 25 This therefore becomes 25/60 The second becomes 3*3= 9 This becomes 9/60 As you're subtracting, you only subtract the numerators. 25-9= 16 Therefore, the answer is 16/60 which can be simplified to 4/10 or 2/5 Hope this helps :)
