4-7х+21≤-9
-7х≤-9-21-4
-7х≤-34
х≥34/7
х≥4 6/7
5*х=42172-7152 5*х=35020 х=35020:5 х=7004 Проверка: 42172-5*7004=7152
<span> 9*х = 189
х=189:9
х=21
х - 428 = 195
х=195+428
х=623</span>
.....…...…….................
<span>-x-2+3(x-3)=3(4-x)-3
-х-2+3х-9=12-3х-3
-х+3х+3х=12-3+2+9
5х=20
х=20:5
х=4</span>