Compare each pair of numbers using <,> or =. A. 56 cm 6 m
B. 7 g 698 mg
C. 19 g .021 k

Can someone explain to me how to do this problem ?

Aplanet of mass m 6.75 x 1024 kg is orbiting in a circular path a star of mass m 2.75 x 1029 kg. the radius of the orbit is r 8.05 x107 km. what is the orbital period (in earth days) of the planet tplanet?

Will you chech and finish these for me, because i am stumped with them.