Given,
Weight of the body in air = 20gf ( Wa)
Weight of the body in water = 18gf ( Ws)
Weight of the body in liquid =18.2gf ( Wl)
Now,
The loss of weight in the water = 20 - 18 or, 2 gf
So the relative density of the body is = Wa / ( wa - ws )
= 20 / 2
= 10
2) The weight loss in liquid = 20 - 18.2 or, 1.8 gf
So the relative density of the liquid is =( Wa - Wl ) / ( Wa - Ws )
= 1.8 / 2
= 0.9
Hope this helps :)