I'm done with the first 1 and 2
I have problem with 3
1)
Calculate, using Newton's law of gravity, the size of the force of attraction between the Earth and a mass of 3.0 kg on the Earth. Data: Distance to the center of Earth from the surface = 6370 km. Mass of Earth = 5.98 1024 kg. Gravitational constant (G = 6.67 times 10−11 Nm2/kg2).
(in N) 2.949×101 N

2)
Calculate, using Newton's law of gravity, the size of the force of attraction between the moon and a mass of 3.0 kg on the earth surface nearest the moon. Data: Distance to the moon from surface of the earth = 376,000 km. Mass of moon = 7.36 times 1022 kg.
(in N) 1.042×10-4 N

3) Calculate, using Newton's law of gravity, the ratio of the strength of the force of attraction of a mass of 3.0 kg on the earth's surface by the sun to that by the moon. Additional Data: Mass of sun =1.99 times 1030 kg. Distance from the sun to the surface of Earth = 1.50 times 108 km.
OK what I did here is this
of course I use
F= G*m1*m2/r^2
G= 6.67*10^-11
m1 sun = 1.99*10^30 kg
m2 = 3 kg
r (d from sun to eath ) = 1.50*10^11 m
I put the stuff I have in the law..
and I got 0.0176 N and it's not right..
well here they ask us.. from moon to sun, so I guess my problem was there ?

So far so good. You just didn't answer what the question was asking for.


Calculate, using Newton's law of gravity, the ratio of the strength of the force of attraction of a mass of 3.0 kg on the earth's surface by the sun to that by the moon.

I got 170 rounded to 3 sf. :)

well yeah , I now got the question .
OK this is what they need
F of the sun (in these question ) / F of the moon (in these question) = the ratio..
but , I did it and I got it also wrong !

Could you post what you did? Maybe we'll spot your mistake :)