0.6(х+7)-0.5(х-3)=6.8
0.6х+4.2-0.5х+1.5=6.8
0.6х-0.5х=6.8-4.2-1.5
0.1х=1.1
х=1.1:0.1
х=11
ОТВЕТ:11
(а²-1)х=а-1