Respuesta :

the fraction is your answer :P so the common denominator seems to be 180, which ends up being 9/180 - 5/180 = 4/180, which simplifies to 1/45 and thats what 1/20-1/36 equals to :P 
Answer is 1/45

(1) Find the LCD for 1/20-1/36 :180 
      1 * 9/180  -  1 * 5/180 
(2) 9/180 - 5/180 = 4/180 = 1/45