OK, let's crack this. We're given 685 and our task is to multiply it by 39. Essentially, we'll be adding 685 to itself 39 times.
Step 1: 0 + 685 = 685
Step 2: 685 + 685 = 1370
Step 3: 1370 + 685 = 2055
Step 4: 2055 + 685 = 2740
Step 5: 2740 + 685 = 3425
Step 6: 3425 + 685 = 4110
Step 7: 4110 + 685 = 4795
Step 8: 4795 + 685 = 5480
Step 9: 5480 + 685 = 6165
Step 10: 6165 + 685 = 6850
Step 11: 6850 + 685 = 7535
Step 12: 7535 + 685 = 8220
Step 13: 8220 + 685 = 8905
Step 14: 8905 + 685 = 9590
Step 15: 9590 + 685 = 10275
Step 16: 10275 + 685 = 10960
Step 17: 10960 + 685 = 11645
Step 18: 11645 + 685 = 12330
Step 19: 12330 + 685 = 13015
Step 20: 13015 + 685 = 13700
Step 21: 13700 + 685 = 14385
Step 22: 14385 + 685 = 15070
Step 23: 15070 + 685 = 15755
Step 24: 15755 + 685 = 16440
Step 25: 16440 + 685 = 17125
Step 26: 17125 + 685 = 17810
Step 27: 17810 + 685 = 18495
Step 28: 18495 + 685 = 19180
Step 29: 19180 + 685 = 19865
Step 30: 19865 + 685 = 20550
Step 31: 20550 + 685 = 21235
Step 32: 21235 + 685 = 21920
Step 33: 21920 + 685 = 22605
Step 34: 22605 + 685 = 23290
Step 35: 23290 + 685 = 23975
Step 36: 23975 + 685 = 24660
Step 37: 24660 + 685 = 25345
Step 38: 25345 + 685 = 26030
Step 39: 26030 + 685 = 26715

So, 685*39 = 26715