1)
5890 - х * 4 = 5390
5890 - 5390 = 4х
500 = 4х
4х = 500
х = 500 : 4
х = 125
проверка:
5890 - 125 * 4 = 5390
5890 - 500 = 5390
5390 = 5390
2)
157 + х * 6 = 25705
6х = 25705 - 157
6х = 25548
х = 25548 : 6
х = 4258
проверка:
157 + 4258 * 6 = 25705
157 + 25548 = 25705
25705 = 25705