To simplify, first combine like terms:

5/6b - 1/3a - 1/6b + 2/3a - 13,4
= (5/6b - 1/6b) - (1/3a - 2/3a) - 13,4
= 4/6b - 1/3a - 13,4
= 2/3b - 1/3a - 13,4

Therefore, 5/6b - 1/3a - 1/6b + 2/3a - 13,4 simplifies to 2/3b - 1/3a - 13,4.