(3 1/2 х - 1 5/14)*42=6
3 1/2 х -1 5/14=6/42
3 1/2 х=2/14+1 5/14
3 1/2 х=1 7/14
х=1 1/2 : 3 1/2
х=3/2 * 2/7
х=3/7
8,2 :х+1 7/12=7 5/18
8,2:х=7 5/18 - 1 7/12
8,2:х=7 10/36 - 1 21/36
8,2:х=5 25/36
8,2:х=5 25/36
х=8,2 :5 25/36
х=41/50 * 36/205
х=18/125=0,144