Question

A star has a mass of 4.3 Msun. Hydrogen gas accounts for 67.9% of the star's mass. What is the mass of all the hydrogen in this star?

Answer 1

65.5 % = 65.5 / 100 = 0.655

So the mass will be 0.655 x 5.9 M_sun

You will need to look up the mass of the Sun in kg.

Your data here is given to 2 and 3 significant figures so you should give your final answer to 2 significant figures.