OK, let's crack this. We're given 869 and our task is to multiply it by 24. Essentially, we'll be adding 869 to itself 24 times.
Step 1: 0 + 869 = 869
Step 2: 869 + 869 = 1738
Step 3: 1738 + 869 = 2607
Step 4: 2607 + 869 = 3476
Step 5: 3476 + 869 = 4345
Step 6: 4345 + 869 = 5214
Step 7: 5214 + 869 = 6083
Step 8: 6083 + 869 = 6952
Step 9: 6952 + 869 = 7821
Step 10: 7821 + 869 = 8690
Step 11: 8690 + 869 = 9559
Step 12: 9559 + 869 = 10428
Step 13: 10428 + 869 = 11297
Step 14: 11297 + 869 = 12166
Step 15: 12166 + 869 = 13035
Step 16: 13035 + 869 = 13904
Step 17: 13904 + 869 = 14773
Step 18: 14773 + 869 = 15642
Step 19: 15642 + 869 = 16511
Step 20: 16511 + 869 = 17380
Step 21: 17380 + 869 = 18249
Step 22: 18249 + 869 = 19118
Step 23: 19118 + 869 = 19987
Step 24: 19987 + 869 = 20856

So, 869*24 = 20856