[tex]\sf Slope= \frac{y_2-y_1}{x_2-x_1}[/tex]
Where [tex]\sf (x_1,y_1), (x_2,y_2)[/tex] are the two points.
So
[tex]\sf Slope = \frac{ -10-(-5)}{7-2}=\frac{-10+5}{7-2}=\frac{-5}{5}=-1[/tex]
So the slope of (2,-5) and (7,-10) was [tex]\boxed{ -1}[/tex]