1) = 21-5+8=24
2) = 3,7-4+5,3= 5
3) = 1/6 - 5/12 + 7/12 = 2/12 - 5/12 + 7/12 = 4/12 = 1/3
4) = -13-20+32 = -1
5) = -4,5-7+9,5 = -2
6) = -5/8-5/8+1 = -10/8 + 1 = -2/8 = - 1/4
7) = -18-9+5= -22
8) = -0,25-3+2,25 = -1
9) = -2/9-1+8/9 = 6/9 - 1 = -3/9 = -1/3