We also need to know how to calculate a fraction of some number. Whenever you see "a fraction of some number" (like "2/3 of the bananas") we will always multiply the fraction times the number. In our case we will multiply 2/3 times the number of bananas.
When "A" starts there are "x" bananas. When "A" is done there is 2/3 of x or
When "B" starts there are
When "C" starts there are
We are told that after "C" is done that there are 8 bananas. So
We can solve for x by multiplying both sides by 27/8 (or by dividing both sides by 8/27). This gives x = 27. Since x represents the original number of bananas and since that is what we were asked to find, 27 is the answer.