The gravitational effect on other bodies determines the weight (or the mass) of a planet. We must somehow measure the strength of its "tug" on another object in order to use gravity to find the mass of a planet. We can harness Newton's equations to deduce what the mass of the planet must be through observing the time it takes for the satellite to orbit its primary planet.
Given:
Mass of Venus = 4.87 x 1024 kg
= 4986.88
Mass of Jupiter = 1.898 x 1024 kg
= 1943.552
Mass of Jupiter compared to mass of Venus
1943.552 / 4986.88
= 0.3897330595482546
= 0.3897330595482546 x 100%
= 38.97%
So, in this problem, the mass of Jupiter is about 0.39 times the mass of Venus.