а)4х+4х=427 б) 15y-8y=714 в) 9z+z=500
4х+4х=427
8х=427
х=427:8
х=53,375
15у-8у=714
7у=714
у=714:7
у=102
9z+z=500
10z=500
z=500:10
z=50