mass and weight

The max effort she can give = 20g N = 200 N (take g=10 m/s2 on earth)

The weight of the same box on another planet = 20g1
where g1 is the acceleration due to gravity on that planet

Since Jupiter is more massive than earth, g1 on Jupiter is gretaer than g on earth. The weight of the box on Jupiter (=20g1) is therefore greater than 200 N. The girl thus cannot lift it.

Mars is less massive than earth, by similar argument, the weight of the box on Mars is lighter than 200 N. The girl thus can lift it.

max force = mg = 20 * 10 = 200N

g at Mars = 10/3
g at Jupiter = 10 *2.34

THerefore, maximum weight at Mars = 200/10*3 = 60kg
maximum weight at Jupiter = 200 /10 / 2.34 ~ 9kg