Answer:
0.91
Explanation:
The total of all numbers in the diagram is 35 +5 +10 +5 = 55.
The total of the numbers inside one or both circles is 35 +5 +10 = 50.
The probability of choosing a random student from inside one or both circles (plays some instrument) is 50 out of 55, or ...
50/55 ≈ 0.9090909... ≈ 0.91
P(A∪B) ≈ 0.91