Let's roll up our sleeves and solve this. We have 556 and we're going to multiply it by 25, essentially adding 556 to itself 25 times.
Step 1: 0 + 556 = 556
Step 2: 556 + 556 = 1112
Step 3: 1112 + 556 = 1668
Step 4: 1668 + 556 = 2224
Step 5: 2224 + 556 = 2780
Step 6: 2780 + 556 = 3336
Step 7: 3336 + 556 = 3892
Step 8: 3892 + 556 = 4448
Step 9: 4448 + 556 = 5004
Step 10: 5004 + 556 = 5560
Step 11: 5560 + 556 = 6116
Step 12: 6116 + 556 = 6672
Step 13: 6672 + 556 = 7228
Step 14: 7228 + 556 = 7784
Step 15: 7784 + 556 = 8340
Step 16: 8340 + 556 = 8896
Step 17: 8896 + 556 = 9452
Step 18: 9452 + 556 = 10008
Step 19: 10008 + 556 = 10564
Step 20: 10564 + 556 = 11120
Step 21: 11120 + 556 = 11676
Step 22: 11676 + 556 = 12232
Step 23: 12232 + 556 = 12788
Step 24: 12788 + 556 = 13344
Step 25: 13344 + 556 = 13900

So, 556*25 = 13900