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.