Start with
[tex] 8+ 5r=-27 [/tex]
Subtract 8 from both sides:
[tex] 5r = -27-8 = -35 [/tex]
Divide both sides by 5:
[tex] r = -7 [/tex]
Let's check the solution, plugging [tex]r=7[/tex] into the equation:
[tex] 8+5r=-27 \iff 8+5\cdot(-7)=-27 \iff 8-35 = -27 [/tex]
which is true.
