OK, let's crack this. We're given 280 and our task is to multiply it by 48. Essentially, we'll be adding 280 to itself 48 times.
Step 1: 0 + 280 = 280
Step 2: 280 + 280 = 560
Step 3: 560 + 280 = 840
Step 4: 840 + 280 = 1120
Step 5: 1120 + 280 = 1400
Step 6: 1400 + 280 = 1680
Step 7: 1680 + 280 = 1960
Step 8: 1960 + 280 = 2240
Step 9: 2240 + 280 = 2520
Step 10: 2520 + 280 = 2800
Step 11: 2800 + 280 = 3080
Step 12: 3080 + 280 = 3360
Step 13: 3360 + 280 = 3640
Step 14: 3640 + 280 = 3920
Step 15: 3920 + 280 = 4200
Step 16: 4200 + 280 = 4480
Step 17: 4480 + 280 = 4760
Step 18: 4760 + 280 = 5040
Step 19: 5040 + 280 = 5320
Step 20: 5320 + 280 = 5600
Step 21: 5600 + 280 = 5880
Step 22: 5880 + 280 = 6160
Step 23: 6160 + 280 = 6440
Step 24: 6440 + 280 = 6720
Step 25: 6720 + 280 = 7000
Step 26: 7000 + 280 = 7280
Step 27: 7280 + 280 = 7560
Step 28: 7560 + 280 = 7840
Step 29: 7840 + 280 = 8120
Step 30: 8120 + 280 = 8400
Step 31: 8400 + 280 = 8680
Step 32: 8680 + 280 = 8960
Step 33: 8960 + 280 = 9240
Step 34: 9240 + 280 = 9520
Step 35: 9520 + 280 = 9800
Step 36: 9800 + 280 = 10080
Step 37: 10080 + 280 = 10360
Step 38: 10360 + 280 = 10640
Step 39: 10640 + 280 = 10920
Step 40: 10920 + 280 = 11200
Step 41: 11200 + 280 = 11480
Step 42: 11480 + 280 = 11760
Step 43: 11760 + 280 = 12040
Step 44: 12040 + 280 = 12320
Step 45: 12320 + 280 = 12600
Step 46: 12600 + 280 = 12880
Step 47: 12880 + 280 = 13160
Step 48: 13160 + 280 = 13440

So, 280*48 = 13440