Alright, let's solve this math problem step by step. First, we have the number 390. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 104. So, we're going to take the number 390 and add it to itself 104 times.
Step 1: 0 + 390 = 390
Step 2: 390 + 390 = 780
Step 3: 780 + 390 = 1170
Step 4: 1170 + 390 = 1560
Step 5: 1560 + 390 = 1950
Step 6: 1950 + 390 = 2340
Step 7: 2340 + 390 = 2730
Step 8: 2730 + 390 = 3120
Step 9: 3120 + 390 = 3510
Step 10: 3510 + 390 = 3900
Step 11: 3900 + 390 = 4290
Step 12: 4290 + 390 = 4680
Step 13: 4680 + 390 = 5070
Step 14: 5070 + 390 = 5460
Step 15: 5460 + 390 = 5850
Step 16: 5850 + 390 = 6240
Step 17: 6240 + 390 = 6630
Step 18: 6630 + 390 = 7020
Step 19: 7020 + 390 = 7410
Step 20: 7410 + 390 = 7800
Step 21: 7800 + 390 = 8190
Step 22: 8190 + 390 = 8580
Step 23: 8580 + 390 = 8970
Step 24: 8970 + 390 = 9360
Step 25: 9360 + 390 = 9750
Step 26: 9750 + 390 = 10140
Step 27: 10140 + 390 = 10530
Step 28: 10530 + 390 = 10920
Step 29: 10920 + 390 = 11310
Step 30: 11310 + 390 = 11700
Step 31: 11700 + 390 = 12090
Step 32: 12090 + 390 = 12480
Step 33: 12480 + 390 = 12870
Step 34: 12870 + 390 = 13260
Step 35: 13260 + 390 = 13650
Step 36: 13650 + 390 = 14040
Step 37: 14040 + 390 = 14430
Step 38: 14430 + 390 = 14820
Step 39: 14820 + 390 = 15210
Step 40: 15210 + 390 = 15600
Step 41: 15600 + 390 = 15990
Step 42: 15990 + 390 = 16380
Step 43: 16380 + 390 = 16770
Step 44: 16770 + 390 = 17160
Step 45: 17160 + 390 = 17550
Step 46: 17550 + 390 = 17940
Step 47: 17940 + 390 = 18330
Step 48: 18330 + 390 = 18720
Step 49: 18720 + 390 = 19110
Step 50: 19110 + 390 = 19500
Step 51: 19500 + 390 = 19890
Step 52: 19890 + 390 = 20280
Step 53: 20280 + 390 = 20670
Step 54: 20670 + 390 = 21060
Step 55: 21060 + 390 = 21450
Step 56: 21450 + 390 = 21840
Step 57: 21840 + 390 = 22230
Step 58: 22230 + 390 = 22620
Step 59: 22620 + 390 = 23010
Step 60: 23010 + 390 = 23400
Step 61: 23400 + 390 = 23790
Step 62: 23790 + 390 = 24180
Step 63: 24180 + 390 = 24570
Step 64: 24570 + 390 = 24960
Step 65: 24960 + 390 = 25350
Step 66: 25350 + 390 = 25740
Step 67: 25740 + 390 = 26130
Step 68: 26130 + 390 = 26520
Step 69: 26520 + 390 = 26910
Step 70: 26910 + 390 = 27300
Step 71: 27300 + 390 = 27690
Step 72: 27690 + 390 = 28080
Step 73: 28080 + 390 = 28470
Step 74: 28470 + 390 = 28860
Step 75: 28860 + 390 = 29250
Step 76: 29250 + 390 = 29640
Step 77: 29640 + 390 = 30030
Step 78: 30030 + 390 = 30420
Step 79: 30420 + 390 = 30810
Step 80: 30810 + 390 = 31200
Step 81: 31200 + 390 = 31590
Step 82: 31590 + 390 = 31980
Step 83: 31980 + 390 = 32370
Step 84: 32370 + 390 = 32760
Step 85: 32760 + 390 = 33150
Step 86: 33150 + 390 = 33540
Step 87: 33540 + 390 = 33930
Step 88: 33930 + 390 = 34320
Step 89: 34320 + 390 = 34710
Step 90: 34710 + 390 = 35100
Step 91: 35100 + 390 = 35490
Step 92: 35490 + 390 = 35880
Step 93: 35880 + 390 = 36270
Step 94: 36270 + 390 = 36660
Step 95: 36660 + 390 = 37050
Step 96: 37050 + 390 = 37440
Step 97: 37440 + 390 = 37830
Step 98: 37830 + 390 = 38220
Step 99: 38220 + 390 = 38610
Step 100: 38610 + 390 = 39000
Step 101: 39000 + 390 = 39390
Step 102: 39390 + 390 = 39780
Step 103: 39780 + 390 = 40170
Step 104: 40170 + 390 = 40560

So, 390*104 = 40560