You have the following expression:
4 2/6 - 5/6
consider that 5/6 = 2/6 + 3/6, then:
4 2/6 - 5/6 = 4 2/6 - (2/6 + 3/6) = 4 2/6 - 2/6 - 3/6 = 4 3/6 = 4 1/2
Hence, the result is 4 1/2
