Alright, let's solve this math problem step by step. First, we have the number 864. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 19. So, we're going to take the number 864 and add it to itself 19 times.
Step 1: 0 + 864 = 864
Step 2: 864 + 864 = 1728
Step 3: 1728 + 864 = 2592
Step 4: 2592 + 864 = 3456
Step 5: 3456 + 864 = 4320
Step 6: 4320 + 864 = 5184
Step 7: 5184 + 864 = 6048
Step 8: 6048 + 864 = 6912
Step 9: 6912 + 864 = 7776
Step 10: 7776 + 864 = 8640
Step 11: 8640 + 864 = 9504
Step 12: 9504 + 864 = 10368
Step 13: 10368 + 864 = 11232
Step 14: 11232 + 864 = 12096
Step 15: 12096 + 864 = 12960
Step 16: 12960 + 864 = 13824
Step 17: 13824 + 864 = 14688
Step 18: 14688 + 864 = 15552
Step 19: 15552 + 864 = 16416

So, 864*19 = 16416