Let's get this math done. We have 135 and we're going to multiply it by 31. This is the same as taking 135 and adding it to itself 31 times.
Step 1: 0 + 135 = 135
Step 2: 135 + 135 = 270
Step 3: 270 + 135 = 405
Step 4: 405 + 135 = 540
Step 5: 540 + 135 = 675
Step 6: 675 + 135 = 810
Step 7: 810 + 135 = 945
Step 8: 945 + 135 = 1080
Step 9: 1080 + 135 = 1215
Step 10: 1215 + 135 = 1350
Step 11: 1350 + 135 = 1485
Step 12: 1485 + 135 = 1620
Step 13: 1620 + 135 = 1755
Step 14: 1755 + 135 = 1890
Step 15: 1890 + 135 = 2025
Step 16: 2025 + 135 = 2160
Step 17: 2160 + 135 = 2295
Step 18: 2295 + 135 = 2430
Step 19: 2430 + 135 = 2565
Step 20: 2565 + 135 = 2700
Step 21: 2700 + 135 = 2835
Step 22: 2835 + 135 = 2970
Step 23: 2970 + 135 = 3105
Step 24: 3105 + 135 = 3240
Step 25: 3240 + 135 = 3375
Step 26: 3375 + 135 = 3510
Step 27: 3510 + 135 = 3645
Step 28: 3645 + 135 = 3780
Step 29: 3780 + 135 = 3915
Step 30: 3915 + 135 = 4050
Step 31: 4050 + 135 = 4185

So, 135*31 = 4185