18. (-6целых2/15-1целая1/12+5целых1/6): 1/2-3,45+7,14

18. (- 6 2/15 - 1 1/12 + 5 1/6) : 1/2 - 3,45 + 7,14 = - 0,41.

1) - 6 2/15 - 1 1/12 = - (6 8/60 + 1 5/60) = - 7 13/60
2) - 7 13/60 + 5 1/6 = - (7 13/60 - 5 10/60) = - 2 3/60 
3) - 2 3/60 : 1/2 = - 123/60 * 2/1 = - 123/30 = - 4 3/30 = - 4,1
4) - 4,1 - 3,45 = - (4,1 + 3,45) = - 7,55
5) - 7,55 + 7,14 = - (7,55 - 7,14) = - 0,41