Answer:
A) When adding numbers in scientific notation, we must be careful of the exponents.
The Moon's mass can be rewritten as .0734 x 10^24 kg
Now we add the Mass of the Earth: 5.97 x 10^24 kg
and that equals 6.0434 x 10^24 kg
HOWEVER, not all those figures are significant and we have to adjust that combined mass to 6.04 x 10^24 kg.
B) Mass Earth / Mass Moon = 5.97 x 10^24 kg / 7.34 x 10^22 kg =
81.3351498638
So, the Earth is about 81 times more massive than the Moon.
Explanation: