Without delay, let's solve this. We've got 615 and we will be multiplying it by 25, that is, adding 615 to itself 25 times.
Step 1: 0 + 615 = 615
Step 2: 615 + 615 = 1230
Step 3: 1230 + 615 = 1845
Step 4: 1845 + 615 = 2460
Step 5: 2460 + 615 = 3075
Step 6: 3075 + 615 = 3690
Step 7: 3690 + 615 = 4305
Step 8: 4305 + 615 = 4920
Step 9: 4920 + 615 = 5535
Step 10: 5535 + 615 = 6150
Step 11: 6150 + 615 = 6765
Step 12: 6765 + 615 = 7380
Step 13: 7380 + 615 = 7995
Step 14: 7995 + 615 = 8610
Step 15: 8610 + 615 = 9225
Step 16: 9225 + 615 = 9840
Step 17: 9840 + 615 = 10455
Step 18: 10455 + 615 = 11070
Step 19: 11070 + 615 = 11685
Step 20: 11685 + 615 = 12300
Step 21: 12300 + 615 = 12915
Step 22: 12915 + 615 = 13530
Step 23: 13530 + 615 = 14145
Step 24: 14145 + 615 = 14760
Step 25: 14760 + 615 = 15375

So, 615*25 = 15375