So, if the man weight 900 newtons on Earth then that means, using F=ma, that the mass of the man is approximately 91.84 kg. This is because 900N=m(9.8m/s^2), and so it follows that 900/9.8=91.84. Using the man's found mass we then plug this into F=ma again. It follows that F=(91.84)(25.9)=2378.57N. This means that the man "weighs" 2378.57 Newtons on Jupiter, or about 2.5x as great as his weight on Earth. This makes sense, considering that 25.9/9.8 is approximately equal to 2.64.
