OK, let's crack this. We're given 315 and our task is to multiply it by 31. Essentially, we'll be adding 315 to itself 31 times.
Step 1: 0 + 315 = 315
Step 2: 315 + 315 = 630
Step 3: 630 + 315 = 945
Step 4: 945 + 315 = 1260
Step 5: 1260 + 315 = 1575
Step 6: 1575 + 315 = 1890
Step 7: 1890 + 315 = 2205
Step 8: 2205 + 315 = 2520
Step 9: 2520 + 315 = 2835
Step 10: 2835 + 315 = 3150
Step 11: 3150 + 315 = 3465
Step 12: 3465 + 315 = 3780
Step 13: 3780 + 315 = 4095
Step 14: 4095 + 315 = 4410
Step 15: 4410 + 315 = 4725
Step 16: 4725 + 315 = 5040
Step 17: 5040 + 315 = 5355
Step 18: 5355 + 315 = 5670
Step 19: 5670 + 315 = 5985
Step 20: 5985 + 315 = 6300
Step 21: 6300 + 315 = 6615
Step 22: 6615 + 315 = 6930
Step 23: 6930 + 315 = 7245
Step 24: 7245 + 315 = 7560
Step 25: 7560 + 315 = 7875
Step 26: 7875 + 315 = 8190
Step 27: 8190 + 315 = 8505
Step 28: 8505 + 315 = 8820
Step 29: 8820 + 315 = 9135
Step 30: 9135 + 315 = 9450
Step 31: 9450 + 315 = 9765

So, 315*31 = 9765