On selling a watch at 4/5 of the marked price there is a loss of 10 p…

We use the following abbreviations,

Marked Price = M

Cost Price = C 

Selling Price = S

According to the question,

  M  :  S  :  C

  5  :  4

         9   : 10                             (10% = \(\frac{1}{10}\))

________________

 45 : 36  : 40

Ratio of M : C = 45 : 40 = 9 : 8