If john ate 1/6 then 5/6 of the cake is left.
Susan ate 1/5 of 5/6=1/6. So, she also ate 1/6 of the cake. Now, 5/6 - 1/6 = 4/6 of the cake is left.
Chan ate 1/4 of 4/6=1/6. So, he also ate 1/6 of the cake. Now, 4/6 - 1/6 = 3/6 of the cake is left.
Cindy ate 1/3 of 3/6=1/6. So, she also ate 1/6 of the cake. Now, 3/6 - 1/6 = 2/6 of the cake is left.
Luigi ate 1/2 of 2/6=1/6. So, he also ate 1/6 of the cake. Now, 2/6 - 1/6 = 1/6 of the cake is left.
Everyone ate 1/6 of the cake. They started with a whole cake or 6/6. So, 6/6 - 5/6 eaten equals 1/6 of the whole cake is left.
Remember "of" means to multiply. Don't forget to simplify diagonally to make the math easier to follow.
example...1/5 * 5/6 you can simplify the 5's because one is a numerator and the other is a denominator and the GCF is 5. Then, multiply straight across.