can someone check if the answer is right?

for a) I divided $\displaystyle 100x10^9$ by $\displaystyle 10^7$ and got 10,000.suppose that $\displaystyle 1$ in every $\displaystyle 10^7$ stars orbited by an earth-like planet:

a) if there are $\displaystyle 100 x 10^9$ stars in the milky way galaxy, how many of its planets are earthlike?

b) if there are $\displaystyle 100x10^9$ galaxies in the universe, how many of its planets are earth-like?

for b) I divided $\displaystyle 100x10^9$ by $\displaystyle 10,000$ and got 10,000,000.