(х-2/7)/2/7=48,3/0,7
0,7(х-2/7)=48,3*2/7
0,7(х-2/7)=483/10*2/7
7/10(х-2/7)=69/5
х-2/7=69/5:7/10
х-2/7=138/7
х=138/7+2/7
х=140/7
х=20
1,8/6,8=0,042/(1 1/6х+0,042)
1,8(1 1/6х+0,042)=6,8*0,042
1,8(1 1/6х+0,042)=0,2856
1 1/6х+0,042=0,2856:1,8
7/6х+0,042=357/1250:9/5
7/6х+0,042=357/2250
7/6х=357/2250-42/1000
7/6х=1428/9000-378/9000
7/6х=21/180
х=21/180:7/6
х=1/10