Without delay, let's solve this. We've got 680 and we will be multiplying it by 28, that is, adding 680 to itself 28 times.
Step 1: 0 + 680 = 680
Step 2: 680 + 680 = 1360
Step 3: 1360 + 680 = 2040
Step 4: 2040 + 680 = 2720
Step 5: 2720 + 680 = 3400
Step 6: 3400 + 680 = 4080
Step 7: 4080 + 680 = 4760
Step 8: 4760 + 680 = 5440
Step 9: 5440 + 680 = 6120
Step 10: 6120 + 680 = 6800
Step 11: 6800 + 680 = 7480
Step 12: 7480 + 680 = 8160
Step 13: 8160 + 680 = 8840
Step 14: 8840 + 680 = 9520
Step 15: 9520 + 680 = 10200
Step 16: 10200 + 680 = 10880
Step 17: 10880 + 680 = 11560
Step 18: 11560 + 680 = 12240
Step 19: 12240 + 680 = 12920
Step 20: 12920 + 680 = 13600
Step 21: 13600 + 680 = 14280
Step 22: 14280 + 680 = 14960
Step 23: 14960 + 680 = 15640
Step 24: 15640 + 680 = 16320
Step 25: 16320 + 680 = 17000
Step 26: 17000 + 680 = 17680
Step 27: 17680 + 680 = 18360
Step 28: 18360 + 680 = 19040

So, 680*28 = 19040