Answer:
r = 11
Step-by-step explanation:
The formula of a slope:
[tex]m=\dfrac{y_2-y_1}{x_2-x_1}[/tex]
We have the slope m = 3/4 and the points (r, 4) and (7, 1). Substitute:
[tex]\dfrac{1-4}{7-r}=\dfrac{3}{4}[/tex]
[tex]dfrac{-3}{7-r}=\dfrac{3}{4}[/tex] cross multiply
[tex]3(7-r)=(-3)(4)[/tex] divide both sides by 3
[tex]7-r=-4[/tex] subtract 7 from both sides
[tex]-r=-11[/tex] change the signs
[tex]\boxed{r=11}[/tex]
