Without delay, let's solve this. We've got 809 and we will be multiplying it by 25, that is, adding 809 to itself 25 times.
Step 1: 0 + 809 = 809
Step 2: 809 + 809 = 1618
Step 3: 1618 + 809 = 2427
Step 4: 2427 + 809 = 3236
Step 5: 3236 + 809 = 4045
Step 6: 4045 + 809 = 4854
Step 7: 4854 + 809 = 5663
Step 8: 5663 + 809 = 6472
Step 9: 6472 + 809 = 7281
Step 10: 7281 + 809 = 8090
Step 11: 8090 + 809 = 8899
Step 12: 8899 + 809 = 9708
Step 13: 9708 + 809 = 10517
Step 14: 10517 + 809 = 11326
Step 15: 11326 + 809 = 12135
Step 16: 12135 + 809 = 12944
Step 17: 12944 + 809 = 13753
Step 18: 13753 + 809 = 14562
Step 19: 14562 + 809 = 15371
Step 20: 15371 + 809 = 16180
Step 21: 16180 + 809 = 16989
Step 22: 16989 + 809 = 17798
Step 23: 17798 + 809 = 18607
Step 24: 18607 + 809 = 19416
Step 25: 19416 + 809 = 20225

So, 809*25 = 20225