OK, let's crack this. We're given 355 and our task is to multiply it by 20. Essentially, we'll be adding 355 to itself 20 times.
Step 1: 0 + 355 = 355
Step 2: 355 + 355 = 710
Step 3: 710 + 355 = 1065
Step 4: 1065 + 355 = 1420
Step 5: 1420 + 355 = 1775
Step 6: 1775 + 355 = 2130
Step 7: 2130 + 355 = 2485
Step 8: 2485 + 355 = 2840
Step 9: 2840 + 355 = 3195
Step 10: 3195 + 355 = 3550
Step 11: 3550 + 355 = 3905
Step 12: 3905 + 355 = 4260
Step 13: 4260 + 355 = 4615
Step 14: 4615 + 355 = 4970
Step 15: 4970 + 355 = 5325
Step 16: 5325 + 355 = 5680
Step 17: 5680 + 355 = 6035
Step 18: 6035 + 355 = 6390
Step 19: 6390 + 355 = 6745
Step 20: 6745 + 355 = 7100

So, 355*20 = 7100