OK, let's crack this. We're given 400 and our task is to multiply it by 30. Essentially, we'll be adding 400 to itself 30 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

So, 400*30 = 12000