2. 240:3+7-2 240: (3+7)-2 640:8-4-5 640:(8-4)-5

240 : 3 + 7 - 2 = 80 + 7 - 2 = 85

240 : (3 + 7) - 2 = 240 : 10 - 2 = 24 - 2 = 22

640 : 8 - 4 * 5 = 80 - 20 = 60

640 : (8 - 4) * 5 = 640 : 4 * 5 = 160 * 5 = 800