х + 320 = 80 * 7
х + 320 = 560
х = 560 - 320
х = 240
240 + 320 = 80 * 7
560 = 560
х - 180 = 240 : 3
х - 180 = 80
х = 80 + 180
х = 260
260 - 180 = 240 : 3
80 = 80
400 - х = 275 + 25
400 - х = 300
х = 400 - 300
х = 100
400 - 100 = 275 + 25
300 = 300
