The first part of this problem is worded poorly. In order for the rest of the problem to make sense, I will assume that 40% participated in track events.

a) Your Venn Diagram will show 2 intersecting circles labelled Track and Field. You will have 22% in the Track circle, 16% in the Field circle, and 18% in the area where the 2 circles intersect. The 22% and 16% are because 40% - 18% = 22% and 34% - 18% = 16%. This way, the sum of the probabilities in each of the circles is correct.

b) From the Venn Diagram, you could just add 22% + 18% + 16% = 56%

Alternatively, you can use the formula P(A U B) = P(A) +P(B) - P(A n B) here A n B is supposed to indicate A intersect B

The number not competing is 1 - P(A U B) = 1 - 56% = 44%