OK, let's work through this together. We're starting with 20 and we're going to multiply it by 141, which means we add 20 to itself 141 times.
Step 1: 0 + 20 = 20
Step 2: 20 + 20 = 40
Step 3: 40 + 20 = 60
Step 4: 60 + 20 = 80
Step 5: 80 + 20 = 100
Step 6: 100 + 20 = 120
Step 7: 120 + 20 = 140
Step 8: 140 + 20 = 160
Step 9: 160 + 20 = 180
Step 10: 180 + 20 = 200
Step 11: 200 + 20 = 220
Step 12: 220 + 20 = 240
Step 13: 240 + 20 = 260
Step 14: 260 + 20 = 280
Step 15: 280 + 20 = 300
Step 16: 300 + 20 = 320
Step 17: 320 + 20 = 340
Step 18: 340 + 20 = 360
Step 19: 360 + 20 = 380
Step 20: 380 + 20 = 400
Step 21: 400 + 20 = 420
Step 22: 420 + 20 = 440
Step 23: 440 + 20 = 460
Step 24: 460 + 20 = 480
Step 25: 480 + 20 = 500
Step 26: 500 + 20 = 520
Step 27: 520 + 20 = 540
Step 28: 540 + 20 = 560
Step 29: 560 + 20 = 580
Step 30: 580 + 20 = 600
Step 31: 600 + 20 = 620
Step 32: 620 + 20 = 640
Step 33: 640 + 20 = 660
Step 34: 660 + 20 = 680
Step 35: 680 + 20 = 700
Step 36: 700 + 20 = 720
Step 37: 720 + 20 = 740
Step 38: 740 + 20 = 760
Step 39: 760 + 20 = 780
Step 40: 780 + 20 = 800
Step 41: 800 + 20 = 820
Step 42: 820 + 20 = 840
Step 43: 840 + 20 = 860
Step 44: 860 + 20 = 880
Step 45: 880 + 20 = 900
Step 46: 900 + 20 = 920
Step 47: 920 + 20 = 940
Step 48: 940 + 20 = 960
Step 49: 960 + 20 = 980
Step 50: 980 + 20 = 1000
Step 51: 1000 + 20 = 1020
Step 52: 1020 + 20 = 1040
Step 53: 1040 + 20 = 1060
Step 54: 1060 + 20 = 1080
Step 55: 1080 + 20 = 1100
Step 56: 1100 + 20 = 1120
Step 57: 1120 + 20 = 1140
Step 58: 1140 + 20 = 1160
Step 59: 1160 + 20 = 1180
Step 60: 1180 + 20 = 1200
Step 61: 1200 + 20 = 1220
Step 62: 1220 + 20 = 1240
Step 63: 1240 + 20 = 1260
Step 64: 1260 + 20 = 1280
Step 65: 1280 + 20 = 1300
Step 66: 1300 + 20 = 1320
Step 67: 1320 + 20 = 1340
Step 68: 1340 + 20 = 1360
Step 69: 1360 + 20 = 1380
Step 70: 1380 + 20 = 1400
Step 71: 1400 + 20 = 1420
Step 72: 1420 + 20 = 1440
Step 73: 1440 + 20 = 1460
Step 74: 1460 + 20 = 1480
Step 75: 1480 + 20 = 1500
Step 76: 1500 + 20 = 1520
Step 77: 1520 + 20 = 1540
Step 78: 1540 + 20 = 1560
Step 79: 1560 + 20 = 1580
Step 80: 1580 + 20 = 1600
Step 81: 1600 + 20 = 1620
Step 82: 1620 + 20 = 1640
Step 83: 1640 + 20 = 1660
Step 84: 1660 + 20 = 1680
Step 85: 1680 + 20 = 1700
Step 86: 1700 + 20 = 1720
Step 87: 1720 + 20 = 1740
Step 88: 1740 + 20 = 1760
Step 89: 1760 + 20 = 1780
Step 90: 1780 + 20 = 1800
Step 91: 1800 + 20 = 1820
Step 92: 1820 + 20 = 1840
Step 93: 1840 + 20 = 1860
Step 94: 1860 + 20 = 1880
Step 95: 1880 + 20 = 1900
Step 96: 1900 + 20 = 1920
Step 97: 1920 + 20 = 1940
Step 98: 1940 + 20 = 1960
Step 99: 1960 + 20 = 1980
Step 100: 1980 + 20 = 2000
Step 101: 2000 + 20 = 2020
Step 102: 2020 + 20 = 2040
Step 103: 2040 + 20 = 2060
Step 104: 2060 + 20 = 2080
Step 105: 2080 + 20 = 2100
Step 106: 2100 + 20 = 2120
Step 107: 2120 + 20 = 2140
Step 108: 2140 + 20 = 2160
Step 109: 2160 + 20 = 2180
Step 110: 2180 + 20 = 2200
Step 111: 2200 + 20 = 2220
Step 112: 2220 + 20 = 2240
Step 113: 2240 + 20 = 2260
Step 114: 2260 + 20 = 2280
Step 115: 2280 + 20 = 2300
Step 116: 2300 + 20 = 2320
Step 117: 2320 + 20 = 2340
Step 118: 2340 + 20 = 2360
Step 119: 2360 + 20 = 2380
Step 120: 2380 + 20 = 2400
Step 121: 2400 + 20 = 2420
Step 122: 2420 + 20 = 2440
Step 123: 2440 + 20 = 2460
Step 124: 2460 + 20 = 2480
Step 125: 2480 + 20 = 2500
Step 126: 2500 + 20 = 2520
Step 127: 2520 + 20 = 2540
Step 128: 2540 + 20 = 2560
Step 129: 2560 + 20 = 2580
Step 130: 2580 + 20 = 2600
Step 131: 2600 + 20 = 2620
Step 132: 2620 + 20 = 2640
Step 133: 2640 + 20 = 2660
Step 134: 2660 + 20 = 2680
Step 135: 2680 + 20 = 2700
Step 136: 2700 + 20 = 2720
Step 137: 2720 + 20 = 2740
Step 138: 2740 + 20 = 2760
Step 139: 2760 + 20 = 2780
Step 140: 2780 + 20 = 2800
Step 141: 2800 + 20 = 2820

So, 20*141 = 2820