11/26 chance that the student plays both instruments.
First, add the amount of students that just play flute or piano:
3 + 5 = 8
Then add 8 to the amount that does not play either instrument:
8 + 7 = 15
Then do:
26 - 15 = 11
Then place 11 over the amount of people:
11/26
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C) 3.824 + 4.765 + 1.732 > 3.81 + 4.77 + 3.80
This cannot be solved unless you provide the picture for further answering.
Do the opposite: times 3 and square it.
(3*0.001)² = 0.000009