Question 875557
{{{(1/8)2^(-3r) = 2^(-r)}}}
{{{(2^(-3))2^(-3r) = 2^(-r)}}}
{{{ 2^(-3r - 3) = 2^(-r)}}}
      -3r-3 = -r
         -3 = 2r
         -3/2 = r