Sure thing, let's get straight to it. We start with 243 and we're going to multiply it by 20, which means adding 243 to itself 20 times.
Step 1: 0 + 243 = 243
Step 2: 243 + 243 = 486
Step 3: 486 + 243 = 729
Step 4: 729 + 243 = 972
Step 5: 972 + 243 = 1215
Step 6: 1215 + 243 = 1458
Step 7: 1458 + 243 = 1701
Step 8: 1701 + 243 = 1944
Step 9: 1944 + 243 = 2187
Step 10: 2187 + 243 = 2430
Step 11: 2430 + 243 = 2673
Step 12: 2673 + 243 = 2916
Step 13: 2916 + 243 = 3159
Step 14: 3159 + 243 = 3402
Step 15: 3402 + 243 = 3645
Step 16: 3645 + 243 = 3888
Step 17: 3888 + 243 = 4131
Step 18: 4131 + 243 = 4374
Step 19: 4374 + 243 = 4617
Step 20: 4617 + 243 = 4860

So, 243*20 = 4860