To convert minutes in hours, you have to divide by 60.
We can distribute this division in a smart way: since [tex] 60=6\times 10[/tex], we have
[tex] \dfrac{19.2\times 10^8}{6\times 10} = \dfrac{19.2}{6} \cdot \dfrac{10^8}{10} = 3.2 \cdot 10^7 [/tex]
