8. $\frac{2}{r + 4}=\frac{4}{r}$

Explanation:

Step1: Cross - multiply

$2r = 4(r + 4)$

Step2: Expand the right - hand side

$2r=4r + 16$

Step3: Move terms with $r$ to one side

$2r-4r=16$

Step4: Combine like terms

$- 2r=16$

Step5: Solve for $r$

$r=-8$

Answer:

$r = - 8$