Respuesta :

gmany

The formula of a slope:

[tex]m=\dfrac{y_2-y_1}{x_2-x_1}[/tex]

We have (5, r), (-2, 13) and m = -1.

Substitute:

[tex]\dfrac{13-r}{-2-5}=-1\\\\\dfrac{13-r}{-7}=-1\qquad|\cdot(-7)\\\\13-r=7\qquad|-13\\\\-r=-6\to\boxed{r=6}[/tex]

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