2,1a-(2/7+a)+(5/14-0,8a)=2,1a-2/7-a+5/14-0,8a=2 7/70a-20/70-a+25/70-56/70a=91/70a+5/70-a=1,3a+1/14-a.
2,1a-(2/7+a)+(5/14-0,8a)=2,1a-2/7-a+5/14-0,8a=2 7/70a-20/70-a+25/70-56/70a=91/70a+5/70-a=1,3a+1/14-a.