I'm sure this is a super easy problem, but I've been out of school for five years and didn't take much math my first time since I received a B.A. So I just need a little help getting a jumpstart back into it. I've worked this problem over and over just can't get it to go. Thanks for your help.
Assume that 170 surveys are completed. Of those surveyed, 88 responded positively to effectiveness, 93 responded positively to side effects, and 80 responded positively to cost. Also, 47 responded positively to both effectiveness and side effects, 37 to effectiveness and cost, 47 to side effects and cost, and 20 to none of the items. How many responded to all three?