Remember that the equation for gravitational potential energy is PE = mgy, where PE = potential energy, m=mass, g=acceleration of gravity, and y=distance above your reference level.
You know that PE = 137200J, y = 200m, and g = 9.8 [tex]m/s^{2}[/tex]. Plug these values into the equation and solve for m:
[tex]PE = mgy\\
137200\:J = m(9.8 \: m/s^{2})(200\:m)\\
m = 70 kg[/tex]
The mass of the skier is 70kg.
