The amount of matter in an object is said to be its mass. The SI base unit of mass is kilograms i.e. [tex]kg[/tex].
The mass of the object = [tex]50.0 lbs[/tex] (given)
For converting lbs to kg:
[tex]1 lb = 0.453592 kg[/tex]
So, [tex]50 lbs = 50\times 0.453592 kg = 22.6796 kg \simeq 22.68 kg[/tex]
Hence, the mass of [tex]50.0lbs[/tex] object in kilograms is [tex]22.68 kg[/tex].