You want to make 1/3 and 5/6 have the same denominator so you multiply both the numerator and denominator of 1/3 by 2 to get 2/6. You plug that back into your equation to get: (2/6 - 5/6) / 5/6. 2/6 - 5/6 is -3/6. -3/6 divided by 5/6 is -3/6 multiplied by 6/5 which is -3/5.
