Mass of earth is

Mass of the Earth $=5.97 \times 10^{24} \mathrm{~kg}$

Now, $5.97 \times 10^{24}=5.97 \times 10^{(2+22)}=5.97 \times 10^{2} \times 10^{22}=597 \times 10^{22}$

So, the mass of the Earth can also be written as $597 \times 10^{22} \mathrm{~kg}$.

Mass of the Moon $=7.35 \times 10^{22} \mathrm{~kg}$

Sum of the masses of the Earth and the Moon: $=\left(597 \times 10^{22}\right)+\left(7.35 \times 10^{22}\right)=(597+7.35) \times 10^{22}=604.35 \times 10^{22} \mathrm{~kg}$

$=6.0435 \times 100 \times 10^{22}=6.0435 \times 10^{2} \times 10^{22}=6.0435 \times 10^{(2+22)}=6.0435 \times 10^{24} \mathrm{~kg}$