#Zkj

1)C=5/18+8/19-7/21+(-10/36+11/19+1/3)-5/8

=5/18+8/19-7/21-10/36+11/19+1/3-5/8

=(5/18-10/36)+(8/19+11/19)+(-7/21+1/3)-5/8

=(5/18-5/18)+1+(-1/3+1/3)-5/8

=0+1+0-5/8

=1-5/8

=3/8

2)E=1/13+(-5/18-1/13+12/17)-(12/17-5/18+7/5)

=1/13-5/18-1/13+12/17-12/17+5/18-7/5

=(1/13-1/13)+(-5/18+5/18)+(12/17-12/17)-7/5

=0+0+0-7/5

=-7/5

3)F=15/14-(17/23-80/87+5/4)+(17/23-15/14+1/4)

=15/14-17/23+80/87-5/4+17/23-15/14+1/4

=(15/14-15/14)+(-17/23+17/23)+80/87+(-5/4+1/4)

=0+0+80/87-1

=-7/87

4)G=1/25-4/27+(-23/27+  -1/25-5/43)+5/43-4/7

=1/25-4/27-23/27-1/25-5/43+5/43-4/7

=(1/25-1/25)+(-4/27-23/27)+(-5/43+5/43)-4/7

=0-1+0-4/7

=-11/7

5)H=4/15-23/28-(-23/28+  -11/15-29/27)-2/27

=4/15-23/28+23/28+11/15+29/27-2/27

=(4/15+11/15)+(-23/28+23/28)+(29/27-2/27)

=1+0+1

=2

6)K=1/16-5/21+(-1/16+  -3/5-  -5/21)+  -2/5+3/4

=1/16-5/21-1/16-3/5+5/21-2/5+3/4

=(1/16-1/16)+(-5/21+5/21)+(-3/5-2/5)+3/4

=0+0-1+3/4

=-1/4