OK, let's work through this together. We're starting with 603 and we're going to multiply it by 40, which means we add 603 to itself 40 times.
Step 1: 0 + 603 = 603
Step 2: 603 + 603 = 1206
Step 3: 1206 + 603 = 1809
Step 4: 1809 + 603 = 2412
Step 5: 2412 + 603 = 3015
Step 6: 3015 + 603 = 3618
Step 7: 3618 + 603 = 4221
Step 8: 4221 + 603 = 4824
Step 9: 4824 + 603 = 5427
Step 10: 5427 + 603 = 6030
Step 11: 6030 + 603 = 6633
Step 12: 6633 + 603 = 7236
Step 13: 7236 + 603 = 7839
Step 14: 7839 + 603 = 8442
Step 15: 8442 + 603 = 9045
Step 16: 9045 + 603 = 9648
Step 17: 9648 + 603 = 10251
Step 18: 10251 + 603 = 10854
Step 19: 10854 + 603 = 11457
Step 20: 11457 + 603 = 12060
Step 21: 12060 + 603 = 12663
Step 22: 12663 + 603 = 13266
Step 23: 13266 + 603 = 13869
Step 24: 13869 + 603 = 14472
Step 25: 14472 + 603 = 15075
Step 26: 15075 + 603 = 15678
Step 27: 15678 + 603 = 16281
Step 28: 16281 + 603 = 16884
Step 29: 16884 + 603 = 17487
Step 30: 17487 + 603 = 18090
Step 31: 18090 + 603 = 18693
Step 32: 18693 + 603 = 19296
Step 33: 19296 + 603 = 19899
Step 34: 19899 + 603 = 20502
Step 35: 20502 + 603 = 21105
Step 36: 21105 + 603 = 21708
Step 37: 21708 + 603 = 22311
Step 38: 22311 + 603 = 22914
Step 39: 22914 + 603 = 23517
Step 40: 23517 + 603 = 24120

So, 603*40 = 24120