Hi there!
We know that the acceleration due to gravity is given by:
[tex]g = \frac{Gm_o}{r^2}[/tex]
We can plug in the given values assuming that the above equation represents the earth's gravitational acceleration:
[tex]g_{planet} = \frac{G(2m)}{(3r)^2} = \frac{2}{9}(\frac{Gm}{r})[/tex]
Since the acceleration due to gravity of this other planet is 2/9th of the acceleration due to gravity on earth, the weight:
W = mg, will also be 2/9ths of that of earth. The correct answer is C.