slope is rise over run

so

r-7 = 1

-2-6 2

we start by simplifying as much as we can

r-7 = 1

-8 2

next we get rid of the denominators by cross multiplying. we multiply the bottoms by the tops on the other side of the equation

2(r-7)=-8*1

then simplify

2(r-7)=-8

then we distribute the 2 a(b+c)=ab+ac

2r-2*7=-8

2r-14=-8

then cancel the 14 by adding 14 to both sides

2r-14+14=-8+14

2r=6

then cancel the 2 by dividing both sides by 2

2r/2=6/6

r=3

so r has to be 3

did you understand if you have any questions please comment.