Given that:
It took 30 minutes to clean off 6 desks, let us now solve the amount of desks to clean off in 1 hour.
Therefore,
[tex]30mins\rightarrow hr=\frac{30}{60}hr=\frac{1}{2}hr[/tex]Thus,
[tex]\begin{gathered} \frac{1}{2}hr=6desks \\ \therefore1hr=\frac{6desks}{\frac{1}{2}}=6\div\frac{1}{2}=6\times\frac{2}{1}=12desks \end{gathered}[/tex]Therefore, it took him/her 1 hour to clean off 12desks.
Hence, the amount of hours it will take to clean off 126 desks will be
[tex]\frac{126desks}{12desk}\times1hr=10\frac{1}{2}hours[/tex]Therefore, the answer is
[tex]10\frac{1}{2}hours[/tex]
