S1 question

Imagine it is a spinner that lands on either 1,3,5 or 7 and you have the probabilities of it landing on each of those numbers. It's saying that you have had 3 spins and the total of those spins is 19 so you need to find all the possible combinations of three spins to get 19 in total (e.g. 7+7+5, the probably of that is 0.1x0.1x0.2) work out the probability of each of these combinations and add them together. Then work out add together all of the combinations when the first spin was 7. Since its conditional probability you do probability 7 was first divided by the probability of the combinations that you calculated earlier. I think this is what it meant.
Hope this helps 😀