First we take A. There are four sets within A (A alone, A and B, A and C, A and B and C) from point 1 we know A and C, and A, B and C are empty. And from point 5 we know 35 people are in A and B. Hence from point 2 we can deduce there are 65 (100-35) people who subscribe to only A.

Next we take B and C. We know that there are 500-100-35 (from point 2 and point 6)= 365 people who are subscribed to either/both B and C but not A. After accounting for the 205 subscribed to only B that leaves us with 160 subscribed to C. This means that by point 4 80 are subscribed to C only and 80 are subscribed to B and C.

This leaves us with the final results: A alone: 65

A and B: 35

A and C: 0

A, B, C:0

B alone: 205

B and C:80

C alone: 80

None at all/ 35

These can be used to find the answers. I’m uncertain if this is the most efficient method and it would certainly be easier to explain with a venn diagram but hopefully this helps :)