Sure thing! We've got 891 and we're gonna multiply it by 4. That's the same as adding 891 to itself 4 times.
Step 1: 0 + 891 = 891
Step 2: 891 + 891 = 1782
Step 3: 1782 + 891 = 2673
Step 4: 2673 + 891 = 3564

So, 891*4 = 3564