Answer:
a) 33; b) 8; c) 145
Explanation:
There were 29 students in band. This includes the 9 in both band and drama; this leaves 20 in only band.
There were 17 students in drama. This includes the 9 in both band and drama; this leaves 8 in only drama.
There were 70 students sampled; this means that
70-(20+8+9) = 70-37 = 33 students in neither band nor drama.
There were 8 in only drama.
Since there were 29/70 in band, this means the director can assume he will have
29/70(350) = 29/70(350/1) = 10150/350 = 145 to show up the first day.