Bryan's score on a math exam is 20. Jen scored 10 more than Bryan while Sammy scored 2 fewer than Jen. If the math exam has 35 points in all, how many mistakes did Sammy make?
Jen scored 20 + 10 = <<20+10=30>>30 on the exam.
Sammy scored two less, so his score was30 - 2 = <<30-2=28>>28.
Thus, Sammy made 35 - 28 = <<35-28=7>>7 mistakes.
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