There are different methods to approach this problem, but one way is to use a Venn diagram. First, we can draw three intersecting circles to represent the three types of books:
M
/ \
MSR SRF
where M represents mysteries, S represents science fiction, and R represents romance novels. The overlapping parts represent the customers who purchased more than one type of book, and the area where all three circles intersect represents the customers who purchased all three types.
Next, we can fill in the numbers from the survey:
36
/ \
10 14
/ \
3 7
/ \
19
For example, 36 customers purchased mysteries, so we write "36" in the M circle. 14 customers purchased both mysteries and science fiction, so we write "14" in the overlap between M and S. And so on.
Now we can use the Venn diagram to find the answer. We want to know how many customers purchased mysteries but not romance novels. This corresponds to the part of the M circle that is outside the R circle:
36
/ \
10 14
/ \
3 7
/ \
19
To find this number, we need to subtract the customers who purchased both mysteries and romance novels (the overlap between M and R) from the total number of customers who purchased mysteries (the whole M circle):
36 - 10 - 3 = 23
Therefore, 23 customers purchased mysteries but not romance novels.