the probability is 8 over 15.
14 of the musicians play both guitar and drums, 28 play drums, 18 play the guitar.
it means n(g and d)=14, n(d)=28, n(g)=18.
using the formula of union: -
n(g or d) = n(g) + n(d) - n(g and d).
n(g or d) = 18 + 28 - 14.
n(g or d) = 32.
it says 60 musicians applied for a job at a music school. so n(u)=60.
the probability that the applicant who gets the job plays drums or guitar is = n(g or d)/n(u) = 32/60 = 8/15.
hence, the probability is 8 over 15.
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