When the above equation is balanced the coefficients in order are

The reaction is as follow,

                   Ca(OH)₂  +  Al₂(SO₄)₃    →     CaSO₄  +  Al(OH)₃

Ca are balance on both sides, 

There are 2 Al at left side and one at right so, multiply Al(OH)₃ by 2 to balance,
So,
                   Ca(OH)₂  +  Al₂(SO₄)₃    →     CaSO₄  +  2 Al(OH)₃

Now, Ca and Al are balanced, now balance SO₄, which is 3 at left hand side and one at right hand side, so multiply CaSO₄ on right side by 3, so,

                   Ca(OH)₂  +  Al₂(SO₄)₃    →     3 CaSO₄  +  2 Al(OH)₃

Again Ca got imbalance, so multiply Ca(OH)₂ by 3 to balance Ca, So,

                   3 Ca(OH)₂  +  Al₂(SO₄)₃    →     3 CaSO₄  +  2 Al(OH)₃

The Equation is balance now with respect to every element.

Result:
          The Ratio is 3 : 1 : 3 : 2, so, Option-G is correct.