Without delay, let's solve this. We've got 679 and we will be multiplying it by 31, that is, adding 679 to itself 31 times.
Step 1: 0 + 679 = 679
Step 2: 679 + 679 = 1358
Step 3: 1358 + 679 = 2037
Step 4: 2037 + 679 = 2716
Step 5: 2716 + 679 = 3395
Step 6: 3395 + 679 = 4074
Step 7: 4074 + 679 = 4753
Step 8: 4753 + 679 = 5432
Step 9: 5432 + 679 = 6111
Step 10: 6111 + 679 = 6790
Step 11: 6790 + 679 = 7469
Step 12: 7469 + 679 = 8148
Step 13: 8148 + 679 = 8827
Step 14: 8827 + 679 = 9506
Step 15: 9506 + 679 = 10185
Step 16: 10185 + 679 = 10864
Step 17: 10864 + 679 = 11543
Step 18: 11543 + 679 = 12222
Step 19: 12222 + 679 = 12901
Step 20: 12901 + 679 = 13580
Step 21: 13580 + 679 = 14259
Step 22: 14259 + 679 = 14938
Step 23: 14938 + 679 = 15617
Step 24: 15617 + 679 = 16296
Step 25: 16296 + 679 = 16975
Step 26: 16975 + 679 = 17654
Step 27: 17654 + 679 = 18333
Step 28: 18333 + 679 = 19012
Step 29: 19012 + 679 = 19691
Step 30: 19691 + 679 = 20370
Step 31: 20370 + 679 = 21049

So, 679*31 = 21049