Draw a Venn Diagram to visualize the situation:
Notice that the numbers in purple correspond to the total amount of people in the regions P and O, P and Q, P and S, respectively.
Numbers in red correspond to the number of people in each region.
Then, we should find the correct numbers for the regions O, P, Q and S, as well as M, N, R and T so that the total number of people in each group matches the labels.
Let x represent the amount of people in the region P.
Since the total amount of people in regions O and P must be 31, then the amount of people in O must be 31-x.
Similarly, the amount of people in region Q must be 12-x.
Since the amount of people in the region N (African men who are not doctors) is 5 and the total amount of African people is 40, then, we can write down an equation for x, where the sum of the amount of people in regions N, O, P and Q is 40:
[tex]5+(31-x)+x+(12-x)=40[/tex]Solve for x:
[tex]\begin{gathered} \Rightarrow5+31-x+x+12-x=40 \\ \Rightarrow48-x=40 \\ \therefore x=8 \end{gathered}[/tex]Notice that the number of people in region P, which is 8, corresponds to amount of African women who are doctors. Therefore, the answer for part a) is: 8.
To find how many of the men are neither African or doctors, find first the correct amount of people in regions R and T. This can be done by taking into account the total amount of people who are doctors and the total amount of people who are women.
The number of people in regions O, P, R and S must be equal to 110. For that to happen, the number of people in region R must be 41.
The amount of people in region T can be found similarly, and it is equal to 20.
Once the total amount of people in regions N, O, P, Q, R, S and T is known, we can deduce the number of people that must be in region M taking into account that the total amount of people in the conference is 150.
Substract the total amount of people in regions N to S (which is 139) from 150, in order to find the total amount of people in region M:
[tex]150-139=11[/tex]The region M corresponds to men who are neither African or doctors. Therefore, the answer to part b) is 11.
