[tex]The\ point-slope\ formula:y-y_1=m(x-x_1)\\\\m=\frac{3}{2};\ (3;\ 2)\to x_1=3;\ y_1=2\\\\subtitute:\\\\y-2=\frac{3}{2}(x-3)\\\\y-2=\frac{3}{2}x-\frac{9}{2}\ \ \ \ |add\ 2=\frac{4}{2}\ to\ both\ sides\\\\y=\frac{3}{2}x-\frac{5}{2}\\\\(r;-4)\to x=r\ and\ y=-4\\\\subtitute:[/tex]
[tex]-4=\frac{3}{2}r-\frac{5}{2}\ \ \ \ |add\ \frac{5}{2}\ to\ both\ sides\\\\-\frac{8}{2}+\frac{5}{2}=\frac{3}{2}r\\\\-\frac{3}{2}=\frac{3}{2}r\ \ \ \ \ |divide\ both\ sides\ by\ \frac{3}{2}\\\\-1=r\\\\\boxed{r=-1}[/tex]
