first one:
ratio 8 to 9 mean 8/9
360*8/9 = 320 (B)
second one:
s-represent all student s
j-represent student s which have job
s*2/5=j (C)
1. 8/9 = x/360
Multiply both sides by 360
(8/9)(360) = (360/9) * 8 = 40 * 8 = 320
4. 2/5 = j/s multiply both sides by s and we have
(2/5)s = j → j = (2/5)s