Answer :
The sample space of the problem is 300 while the U' is equal to 100 as given. The given diagram also shows A and B separately so we can determine the part where the two coincides. The equation goes
120 + 50 + x + 100 = 300x = 30
Hence the probability is 30/ 300 or 10%
120 + 50 + x + 100 = 300x = 30
Hence the probability is 30/ 300 or 10%