1/18 is left. Thomas has 1/18 left of his book. How? What denominator can 9&6 relate to? 54? Sure, but it could be lower. How about 18? Ok. We have 18 because 9x2 and 6x3 both equal 18...
2/9 becomes 4/18 because 18 divided by 9 is 2. You multiply 2 with the two from 2/9.
1/6 becomes 3/18 because 18 divided by 6 is 3. You then multiply 3 with the one from 1/6.
Put it together and TA-DA... Your answer is 1/18
