Hello! 
4.25 kilograms = C. 4,250 g.
I really hope you found this helpful! :)
        
             
        
        
        
I think x = -12 , if that’s what the questions asking
        
             
        
        
        
well when thinking of gravity you have to think of the size and mass of the object so,
The sun (largest and most mass)
Earth 
Earth's moon
Discover satellite (cause it's tiny and light compared to the sun!)