1 4/21 - 2 5/14 = 25/21 - 33/14 = (25 × 2 - 33 × 3)/42 = (50 - 99)/42 = - 49/42 = - 7/6 = - 1 1/6
4,2 : (1 1/6) = 4 2/10 : (- 1 1/6) = 21/5 : ( - 7/6) = 21/5 * ( - 6/7) = - 18/5 = - 3 3/5
- 8 + 3 3/5 = - 8 + 18/5 = (-8 × 5 + 18 × 1)/5 = (-40 + 18)/5 = - 22/5 = - 4 2/5 = 4,4