Answer:
36 sour candies
Explanation:
Because we know that there are four sour candies to every 5 chocolates, we know the bag can be divided up into ninths, four of those ninths being sour and 5 of those ninths being chocolate. One ninth of 81 is 9, so we know that one ninth is equivilant to nine candies. Because four ninths of the bag are sour, we can multiply one ninth by four to get the final answer. 9*4 is 36, so there are 36 sour candies in the bag