Sure thing! We've got 81 and we're gonna multiply it by 4. That's the same as adding 81 to itself 4 times.
Step 1: 0 + 81 = 81
Step 2: 81 + 81 = 162
Step 3: 162 + 81 = 243
Step 4: 243 + 81 = 324

So, 81*4 = 324