Physics or Chemistry. In a group of 50 students, 7 take all three
subjects, 9 take Physics and Chemistry only, 8 take Maths and Physics
only and 5 take Maths and Chemistry only. Of these 50 students, x take
Maths only, x take Physics only and x + 3 take Chemistry only. Draw
a Venn diagram, find x, and hence find the number taking Maths.