Without delay, let's solve this. We've got 145 and we will be multiplying it by 20, that is, adding 145 to itself 20 times.
Step 1: 0 + 145 = 145
Step 2: 145 + 145 = 290
Step 3: 290 + 145 = 435
Step 4: 435 + 145 = 580
Step 5: 580 + 145 = 725
Step 6: 725 + 145 = 870
Step 7: 870 + 145 = 1015
Step 8: 1015 + 145 = 1160
Step 9: 1160 + 145 = 1305
Step 10: 1305 + 145 = 1450
Step 11: 1450 + 145 = 1595
Step 12: 1595 + 145 = 1740
Step 13: 1740 + 145 = 1885
Step 14: 1885 + 145 = 2030
Step 15: 2030 + 145 = 2175
Step 16: 2175 + 145 = 2320
Step 17: 2320 + 145 = 2465
Step 18: 2465 + 145 = 2610
Step 19: 2610 + 145 = 2755
Step 20: 2755 + 145 = 2900

So, 145*20 = 2900