Add up all the values shown:
64+28+52+56 = 200
This result indicates that there are 200 students total.
Of these 200 total people, there are 28 who are attending both colleges. This is the value shown in the overlapping region of the two circles.
Divide the two values (28 and 200) to get...
28/200 = 0.14 = 14%
The probability as a decimal value is 0.14 which is saying there's a 14% chance of picking someone who goes to both colleges.
Recall that the derivative of a constant is 0.
