Answer:
he paid $37 is the answer for the question
The ratio of the frequency at which he picks blue is 18:32 which simplifies to 9:16 but if you want a percentage its 36%
You would put this into a fraction
so for the salad

and for the fruit

cross multiply and
1. salad: 20% = 115 students
2. Fruit: 24% = 138 students