The difference between the circumference and the diameter of a circle is 24cm. Find the radius

Dear Student, 
          
  We have, 
          
          Circumference - Diameter = 24 cm
    i.e.  (2 * pi * r) - 2r = 24 cm            ( because diameter = 2 * radius = 2 * r)   ( taking radius = r )
           2 * r * (pi - 1 ) = 24 cm
           r * ( pi - 1) = 24/2 cm
          r * ( 22/7 - 1) = 12 cm     ( taking pi = 22/7 )
         r * ( ( 22 - 7 )/7 ) = 12 cm
          r * (15/7) = 12 cm
         r = 12 * (7/15) cm
         r = 5.6 cm 

Therefore the radius of the circle is 5.6 cm.

Hope this information clears your doubts.

Regards