<span>218, 221, 442, 445 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
</span>
2х+10=16
2х=16-10
2х=6
х=6:2
х=3
100-4х=36
100-36=4х
4х=64
х=64:4
х=16
20х-45=55
20х=55+45
20х=100
х=100:20
х=5
4х + 3х = 252
7х = 252
х = 252 : 7
х = 36
Ответ: {36}