1. 6*2/13-х=3*7/13
-х=3*7/13-6*2/13
-х=21/13-12/13
-х=21-12/13
-х=9/13
х=-9/13
2. у=5*8/9=3*5/9
у=3*5/9+5*8/9
у=5/3+40/9
у=15+40/9
у=55/9
у=6*1/9
3. (z+2*7/11)-4*7/11=1*6/11
z+2*4/11-4*4/11=1*6/11
z=1*6/11-2*4/11+4*7/11
z=6/11-8/11+28/11
z=6-8+28/11
z=26/11
z=2*4/11