$\text{ If }x,2x+2\text{, and }3x+3\text{ are first three terms of a G.P. then the fourth term is}$

$x,2x+2,3x+3\text{ are in G.P. Hence }$

$\begin{array}{l}(2x+2{)}^2=x(3x+3)\\ \Rightarrow 4x^2+8x+4=3x^2+3x\\ \Rightarrow x^2+5x+4=0\Rightarrow x=-1,-4\\ \text{ So, the G.P is }-4,-6,-9,\dots \text{ (considering }x=-4\text{, as for }x=-1,2x+2=0\text{ ) }\end{array}$

$\text{ Hence, the fourth term is }-9\times 1.5=-13.5$