15/18 - 2/18 = 13/18
Find the least common multiple of 6 and 9. The LCM is 18. In order to get 18 on the denominator with 6, you have to multiply by 3 because 6 times 3 is 18. You have to multiply 3 to the numerator, so 5 times 3 is 15. Thus, the first fraction is 15/18. To get the second, you need to find what would get you 18 on the denominator with 9. You need 2, so 9 times 2 is 18. You have to multiply 2 to the numerator, so 1 times 2 is 2. Thus, the second fraction is 2/18.
