3 machines can fill 80 boxes in 2 hours
\((\times\frac53)\) \((\times\frac{15}{8})\)
5 machines to fill 150 boxes in x hours
So look machines are inversely propotional more machines less time but boxes are directly proportional more boxes more time:
\(2h.\times\frac35\times\frac{15}{8}=\frac94h.\;(or\;2.25h.)\)
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