evaluate: 3 5/6 - 4 2/6

3 5/6 - 4 2/6 = 

-4 2/6 + 3 5/6 = 

We borrow from the -4 to get -3 - 1 - 2/6, then rewrite as -3 - 6/6 -2/6 which is the same as -3 8/6. Now we can write 

-3 8/6 + 3 5/6 = 

-3 + 3 -8/6 + 5/6 = 

-3/6 = 

-1/2 

:)