Using the symbols in the Venn diagram, we want to find A given that
B = 16
C = 15
D = 30
and given that 25 students don't take any of these courses.
There are 200 students total, so we need to have A plus the total number of students given in the diagram sum to 200. This means
(math only) + (English only) + (biology only) + (math and English, no biology) + (math and biology, no English) + (English and biology, no math) + (all three) + (none of the three) = 200
or
12 + 11 + 16 + 30 + A + 16 + 15 + 25 = 200
Solve for A to get A = 75, making the answer C.