###Human: 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?, ### Assistant: Jen scored 20 + 10 = 30 on the exam.
Sammy scored two less, so his score was30 - 2 = 28.
Thus, Sammy made 35 - 28 = 7 mistakes. 
 So the answer is :  7