one billion is 9 zeros, on million is 6 zeros, thus
[tex]\bf 163,000,000\implies 163\times 10^6
\\\\\\
93,000,000,000\implies 93\times 10^9\\\\
\cfrac{93\times 10^9}{163\times 10^6}\impliedby \textit{hours per year for one adult}
\\\\\\
\cfrac{93\times 10^9\times 10^{-6}}{163}\implie
s \cfrac{93\times 10^{9-6}}{163}\implies \cfrac{93\times 10^3}{163}[/tex]
that's how many hours each adult spent a year... now, how many hours is that per day? well, there are 365 days a year, so, we simply divide it by 365
[tex]\bf \cfrac{\frac{93\times 10^3}{163}}{365}\implies \cfrac{\frac{93\times 10^3}{163}}{\frac{365}{1}}\implies \cfrac{93\times 10^3}{163}\cdot \cfrac{1}{365}\implies \cfrac{93\times 10^3}{163\cdot 365}\quad \cfrac{hours}{day}[/tex]