OK, let's work through this together. We're starting with 39 and we're going to multiply it by 13, which means we add 39 to itself 13 times.
Step 1: 0 + 39 = 39
Step 2: 39 + 39 = 78
Step 3: 78 + 39 = 117
Step 4: 117 + 39 = 156
Step 5: 156 + 39 = 195
Step 6: 195 + 39 = 234
Step 7: 234 + 39 = 273
Step 8: 273 + 39 = 312
Step 9: 312 + 39 = 351
Step 10: 351 + 39 = 390
Step 11: 390 + 39 = 429
Step 12: 429 + 39 = 468
Step 13: 468 + 39 = 507

So, 39*13 = 507