r = 5
calculate the slope m using the gradient formula
m = (y₂ - y₁ ) / (x₂ - x₁ )
with ( x₁, y₁ ) = (6, - 2 ) and (x₂, y₂ ) = (r, - 6)
m = [tex]\frac{-6+2}{r-6}[/tex] = [tex]\frac{-4}{r-6}[/tex] = 4
cross multiply
4(r - 6 ) = - 4
4r - 24 = 4 ( add 24 to both sides and divide by 4 )
4r = 20
r = [tex]\frac{20}{4}[/tex] = 5
