OK, let's work through this together. We're starting with 258 and we're going to multiply it by 40, which means we add 258 to itself 40 times.
Step 1: 0 + 258 = 258
Step 2: 258 + 258 = 516
Step 3: 516 + 258 = 774
Step 4: 774 + 258 = 1032
Step 5: 1032 + 258 = 1290
Step 6: 1290 + 258 = 1548
Step 7: 1548 + 258 = 1806
Step 8: 1806 + 258 = 2064
Step 9: 2064 + 258 = 2322
Step 10: 2322 + 258 = 2580
Step 11: 2580 + 258 = 2838
Step 12: 2838 + 258 = 3096
Step 13: 3096 + 258 = 3354
Step 14: 3354 + 258 = 3612
Step 15: 3612 + 258 = 3870
Step 16: 3870 + 258 = 4128
Step 17: 4128 + 258 = 4386
Step 18: 4386 + 258 = 4644
Step 19: 4644 + 258 = 4902
Step 20: 4902 + 258 = 5160
Step 21: 5160 + 258 = 5418
Step 22: 5418 + 258 = 5676
Step 23: 5676 + 258 = 5934
Step 24: 5934 + 258 = 6192
Step 25: 6192 + 258 = 6450
Step 26: 6450 + 258 = 6708
Step 27: 6708 + 258 = 6966
Step 28: 6966 + 258 = 7224
Step 29: 7224 + 258 = 7482
Step 30: 7482 + 258 = 7740
Step 31: 7740 + 258 = 7998
Step 32: 7998 + 258 = 8256
Step 33: 8256 + 258 = 8514
Step 34: 8514 + 258 = 8772
Step 35: 8772 + 258 = 9030
Step 36: 9030 + 258 = 9288
Step 37: 9288 + 258 = 9546
Step 38: 9546 + 258 = 9804
Step 39: 9804 + 258 = 10062
Step 40: 10062 + 258 = 10320

So, 258*40 = 10320