1) x + 320 = 80 * 7
x + 320 = 560
x = 560 - 320
x = 240
240 + 320 = 80*7
560 = 560
2) x - 180 = 240 / 3
x - 180 = 80
x = 180 + 80
x = 260
260 - 180 = 240 / 3
80 = 80
3) 400 - x = 275 + 25
400 - x = 300
x = 100 - 300
x = 100
400 - 100 = 275 + 25
300 = 300