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 Hi Simon, I see a picture. 
 There are the 1354 people attended exhibition A (inside the circle with an orange perimeter) and the 1427 people attended exhibition B (inside the circle with an brown perimeter). There are some people who attended both, the people in the overlap. I don't know this number so I called it x. You say "79% of people attended both exhibitions" and that gives me an equation 
 If I add 1354 and 1427 I get more than the total number of people since I have counted the x people in the overlap twice. Hence the total number of people is 1354 + 1427 - x. Solve for x. Penny  | ||||||||||||
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