15-13-7+2= 18-12-4+3= -6-3+5-7+1= -4+8-3+2= -5+12-9+1= 2-11+6-7+3= -7+8-4-5+10-1= 11-3+1-6+2-4= 10-7+8-9+2-4= -1-3+4-2-5+10=

1) 15 - 13 - 7 + 2 = 2 - 7 + 2 = - 5 + 2 = -3;

2) 18 - 12 - 4 + 3 = 6 - 4 + 3 = 2 + 3 = 5;

3) -6 - 3 + 5 - 7 + 1 = -9 + 5 - 7 + 1 = -4 - 7 +1 = -11 + 1 = -10;

4) -4 + 8 - 3 + 2 = 4 - 3 + 2 = 1 + 2 = 3;

5) -5 + 12 - 9 + 1 = 7 - 9 + 1 = -2 + 1 = -1;

6) 2 - 11 + 6 - 7 + 3 = -9 + 6 - 7 + 3 = -3 - 7 + 3 = -10 + 3 = -7;

7) -7 + 8 - 4 - 5 + 10 - 1 = 1 - 4 - 5 + 10 - 1 = -3 - 5 + 10 - 1 = -8 + 10 - 1 = 2 - 1 = 1;

8) 11 - 3 + 1 - 6 + 2 - 4 = 8 + 1 - 6 + 2 - 4 = 9 - 6 + 2 = 3 + 2 = 5;

9) 10 - 7 + 8 - 9 + 2 - 4 = 3 + 8 - 9 + 2 - 4 = 11 - 9 + 2 - 4 = 2 + 2 - 4 = 4 - 4 = 0;

10) -1 - 3 + 4 - 2 - 5 + 10 = -4 + 4 - 2 - 5 + 10 = 0 - 2 - 5 + 10 = -7 + 10 = 3.