Question 133117

a) the cost is 0.06x + 19 = (6x+1900)/100 then y =(6x+1900)/100x

Answer: y = (6x+1900)/100x

b) cost = (0.05x+20.2) then average cost is  (0.05x+20.2)/x
   then (0.05x+20.2)/x = 0.2

   then (0.05x+20.2) = 0.2x
   then 0.15x=20.2
   then x=20.2/0.15= 134,6666...

Answer: 135 calls

Are you sure about 20.20 and 0.05? (because solution is not an integer)