**SOLUTION:**

Total=A+B+C− {Sum of Exactly 2 groups members} −2∗A∩B∩C+ Neither

Given:

Total = 600 and as a percentage it is 100%

Neither = 0 __(As all the students have chosen at least one of these three subjects).__

Math (M) = 35%

Science(S) = 40%

History (H) = 50%

Percent chose exactly 2 of these subjects = 18 %

Let M∩H∩S = x

Using the formulae stated above:

100 = 35 + 40 + 50 – 18 -2x + 0

=>100 = 107 - 2x

=> x =7/2 % = 7/200 * 600 = 21 (OPTION D)