In a group of 35 pupils, 11 play the flute only

Question

In a group of 35 pupils, 11 play the flute only.
8 play the piano only.
15 play neither instrument.
A student is selected at random.
What is the probability the student plays both instruments?

Answer 1

Assuming that a 3rd instrument is not in question, P(a randomly selected student plays both the flute and the piano) = 1/35

 

 

35-15=20, 20-11-8=1

 

A²