A small fair charges an admission fee for children and adults. The cost for admission is 3 dollars per adult and 2 dollars per child. On a certain day, total admission fees were 900 dollars , and 350 people attended the fair. How many children attended the fair that day?

Let c be the number of children and a the number of adults. Since 350 people attended, c + a = 350; the admission fees give 2c + 3a = 900. If everyone had paid the child fee, the total would be 2 × 350 = $700, so the extra $200 came from adults paying $1 more each. There were 200 adults, leaving 350 − 200 = 150 children, so the correct choice is 150 children.

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