Sure thing! We've got 400 and we're gonna multiply it by 72. That's the same as adding 400 to itself 72 times.
Step 1: 0 + 400 = 400
Step 2: 400 + 400 = 800
Step 3: 800 + 400 = 1200
Step 4: 1200 + 400 = 1600
Step 5: 1600 + 400 = 2000
Step 6: 2000 + 400 = 2400
Step 7: 2400 + 400 = 2800
Step 8: 2800 + 400 = 3200
Step 9: 3200 + 400 = 3600
Step 10: 3600 + 400 = 4000
Step 11: 4000 + 400 = 4400
Step 12: 4400 + 400 = 4800
Step 13: 4800 + 400 = 5200
Step 14: 5200 + 400 = 5600
Step 15: 5600 + 400 = 6000
Step 16: 6000 + 400 = 6400
Step 17: 6400 + 400 = 6800
Step 18: 6800 + 400 = 7200
Step 19: 7200 + 400 = 7600
Step 20: 7600 + 400 = 8000
Step 21: 8000 + 400 = 8400
Step 22: 8400 + 400 = 8800
Step 23: 8800 + 400 = 9200
Step 24: 9200 + 400 = 9600
Step 25: 9600 + 400 = 10000
Step 26: 10000 + 400 = 10400
Step 27: 10400 + 400 = 10800
Step 28: 10800 + 400 = 11200
Step 29: 11200 + 400 = 11600
Step 30: 11600 + 400 = 12000
Step 31: 12000 + 400 = 12400
Step 32: 12400 + 400 = 12800
Step 33: 12800 + 400 = 13200
Step 34: 13200 + 400 = 13600
Step 35: 13600 + 400 = 14000
Step 36: 14000 + 400 = 14400
Step 37: 14400 + 400 = 14800
Step 38: 14800 + 400 = 15200
Step 39: 15200 + 400 = 15600
Step 40: 15600 + 400 = 16000
Step 41: 16000 + 400 = 16400
Step 42: 16400 + 400 = 16800
Step 43: 16800 + 400 = 17200
Step 44: 17200 + 400 = 17600
Step 45: 17600 + 400 = 18000
Step 46: 18000 + 400 = 18400
Step 47: 18400 + 400 = 18800
Step 48: 18800 + 400 = 19200
Step 49: 19200 + 400 = 19600
Step 50: 19600 + 400 = 20000
Step 51: 20000 + 400 = 20400
Step 52: 20400 + 400 = 20800
Step 53: 20800 + 400 = 21200
Step 54: 21200 + 400 = 21600
Step 55: 21600 + 400 = 22000
Step 56: 22000 + 400 = 22400
Step 57: 22400 + 400 = 22800
Step 58: 22800 + 400 = 23200
Step 59: 23200 + 400 = 23600
Step 60: 23600 + 400 = 24000
Step 61: 24000 + 400 = 24400
Step 62: 24400 + 400 = 24800
Step 63: 24800 + 400 = 25200
Step 64: 25200 + 400 = 25600
Step 65: 25600 + 400 = 26000
Step 66: 26000 + 400 = 26400
Step 67: 26400 + 400 = 26800
Step 68: 26800 + 400 = 27200
Step 69: 27200 + 400 = 27600
Step 70: 27600 + 400 = 28000
Step 71: 28000 + 400 = 28400
Step 72: 28400 + 400 = 28800

So, 400*72 = 28800