Question 170101
This was already solved, I copied it fro Stan H, or stanbon.
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Use a proportion:
[9 infected/15 sampled] = [x infected/all the PCs] 
(9/15) = (x/202)
x = 202(9/15) 
x = 202(3/5)
x = 121.2
Round down to get x = 121 infected PC's out of 202