12 * х + 60 = 18 * 6,
12 * х + 60 = 108,
12 * х = 108 - 60,
12 * х = 48,
х = 48 : 12,
х = 4,
проверка:
12 * 4 + 60 = 108,
48 + 60 = 108,
108 = 108
