х+ 4 1/21=17 5/42
х=17 5/42-4 1/21
х=13 1/14
17 5/42-4 1/21=(17-4)+(5/42-1/21)=13+(5/42-2/42)=13 3/42=13 1/14
х+ 4 1/21=17 5/42
х=17 5/42-4 1/21
х=13 1/14
17 5/42-4 1/21=(17-4)+(5/42-1/21)=13+(5/42-2/42)=13 3/42=13 1/14