fairly straight forward question with a small trick to deceive you, 1000 people surveyed..so the number of a, b or both needs to be divided by 1000, not the 750 who uses product, you also need to account the 250 people who do not use products but are surveyed.

always work from inside out with these venn diagram questions, so 400 people uses a, 400-75-125-125 = 75 ONLY uses A

do the same with B and C, adding them all up, you get 750 out of 1000 people that uses products.

the question asks what perfect of people who either use A, B or both but not C. so you add 75+125+100 = 300 out of 1000= 30%