Answer :
Explanation:
Since we have given that
n(U) = 120, where U denotes universal set ,
n(F) = 45, where F denotes who speak French,
n(S) = 42 , where S denotes who speak Spanish,
n(F∪S)' = 50
n(F∪S) = n(U)-n(F∪S) = 120-50 = 70
Now, we know the formula, i.e.
n(F∪s) = n(F)+n(S)-n(F∩S)
⇒ 70 = 45+42-n(F∩S)
⇒ 70 = 87- n(F∩S)
⇒ 70-87 = -n(F∩S)
⇒ -17 = -n( F∩S)
⇒ 17 = n(F∩S)