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We have that
(36-20) take only Mathematics = 16
(27-20) take only Physics = 7
20 take both....
So (60) - ( 16 + 7 + 20) =
60 - 43 =
17 take neither....
36+27 = 63
63-20 = 43
60-43 = 17.
17 people took neither.
~~Hypotenuisance