1) -2-4 = -6
2) -3+1/3 = -9/3 + 1/3 = -8/3
3) -4+1/5 = -4+0,2 = -3,8
4) 5/7+4/8 = 40/56+28/56 = 68/56
5) 2/3+5/6 = 12/18+15/18 = 27/18 = 1,5
6) 2/3-5/6 = 12/18-15/18 = -3/18
7) -2/3+5/6 = -12/18 + 15/18 = 3/18
8) -2+5/6 = -12/6+5/6 = -7/6
9) -5+7 = 2
10) -7+4 = -3
11) -7-4 = -11
