Answer:
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Step-by-step explanation:
Given

Required
Determine 
We know that:

This gives:


Collect like terms


Take square roots


By tan identity


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It would be 20
To get this answer you would add up all the answer then divide it by how many numbers there are
18+23+10+39+22+17+16+15= 160
160/8 = 20
Total people in the cafeteria = 7 + 48 + 45 = 100
There are 45 boys.
The probability would be the number of boys over the total number of people:
45/100, which simplifies to 9/20