OK, let's work through this together. We're starting with 277 and we're going to multiply it by 15, which means we add 277 to itself 15 times.
Step 1: 0 + 277 = 277
Step 2: 277 + 277 = 554
Step 3: 554 + 277 = 831
Step 4: 831 + 277 = 1108
Step 5: 1108 + 277 = 1385
Step 6: 1385 + 277 = 1662
Step 7: 1662 + 277 = 1939
Step 8: 1939 + 277 = 2216
Step 9: 2216 + 277 = 2493
Step 10: 2493 + 277 = 2770
Step 11: 2770 + 277 = 3047
Step 12: 3047 + 277 = 3324
Step 13: 3324 + 277 = 3601
Step 14: 3601 + 277 = 3878
Step 15: 3878 + 277 = 4155

So, 277*15 = 4155