Answer
$4.1\cdot10^{21}$
Work Step by Step
Convert both measures to meters:
$r_H=0.37\ A^{\circ}\cdot \frac{1\ m}{10^{10}\ A^{\circ}}=0.37\cdot10^{-10}\ m$
$r_O=1.5\cdot10^8\ km\cdot\frac{10^3\ m}{1\ km}=1.5\cdot10^{11}\ m$
Find their ratio:
$\dfrac{r_O}{r_H}=\dfrac{1.5\cdot10^{11}\ m}{0.37\cdot10^{-10}\ m}$
$\dfrac{r_O}{r_H}=4.1\cdot10^{21}$
