Question

While earth has one moon Jupiter has dozens of moon of many sizes for example the moon Leda has a mass of 10,940,279,561,609,500 kg while the moon Europa has a mass of 47,998,438,387,492,700,000,000 kg about what part of europas mass is represented by ledas mass

Answer 1

You could sit down with several pencils and a whole pad of paper, and
divide Leda's mass by Europa's mass.  But it's probably good enough
to provide an answer that's correct to 2 or 3 significant figures, and
there's a much easier way to do that:

Leda's mass . . . . approx.  1.094 x 10¹⁶

Europa's mass . . . . approx. 4.8 x 10²²

Leda's mass is about  (1.094 x 10¹⁶) / (4.8 x 10²²) of Europa's mass.

       (1.094 x 10¹⁶) / (4.8 x 10²²) = 2.28 x 10⁻⁷

Leda's mass is approx.  0.000 000 228  of Europa's mass.