Question

If P and Q are finite sets where n(Q) = 90 and n(P⋂Q) = 30 , n(P⋃Q) = 108 find n(P-Q):​

Answer 1

Answer:

we have a formula

n(PUQ) = n(P) + n(Q) - n(P⋂Q)

from that we get

108 = x + 90 - 30

108 + 30 = x + 90

138 - 90 = x

x = 48

therefore n(P) = 48

we have another formula

n(P-Q) = n(P) - n(P⋂Q)

from that

n(P-Q) = 48 - 30

n(P-Q) = 18

THEREFORE n(P-Q) = 18