The weight of an object is the product of its mass and the acceleration of gravity.
If g[e] is the acceleration of gravity on earth, and g[M] the same for Mars and g[m] the same for the moon,
then m[M]=m[e]g[M]/g[e] and m[m]=m[e]g[m]/g[e] where m[ ] denotes mass. Note that weight=mg (measured in newtons) while mass is in kilograms.
If g[M]=g[e]/3 and g[m]=g[e]/6 approximately. Then the weight of an object on Mars will be about a third of what it is on earth, while on the moon it would be about a sixth of what it is on earth.
