Ammonia, NH3 is a polar molecule, and as such, would be more soluble in water than in carbon tetrachloride. Water is also polar, and carbon tetrachloride is non polar. It is difficult to draw Lewis structures here, but you can look them up. What you will find is that NH3 is polar because the N has a lone pair of electrons, and the hydrogen atoms do NOT lie in the plane of the paper. The N is partially negative, the H atoms are partially positive, and this creates a dipole. Same is true for water. Carbon tetrachloride is completely non polar.