Question

a class of 30 music students includes 13 who play the piano, 15 who play the guitar, and 5 who play both the piano and
the guitar.

how many students in the class play neither instrument?

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Explanation:

Step1: Use inclusion-exclusion principle

Number playing piano or guitar: $13 + 15 - 5 = 23$

Step2: Calculate neither instrument

Total students minus those playing either: $30 - 23 = 7$

Answer:

7