OK, let's work through this together. We're starting with 259 and we're going to multiply it by 15, which means we add 259 to itself 15 times.
Step 1: 0 + 259 = 259
Step 2: 259 + 259 = 518
Step 3: 518 + 259 = 777
Step 4: 777 + 259 = 1036
Step 5: 1036 + 259 = 1295
Step 6: 1295 + 259 = 1554
Step 7: 1554 + 259 = 1813
Step 8: 1813 + 259 = 2072
Step 9: 2072 + 259 = 2331
Step 10: 2331 + 259 = 2590
Step 11: 2590 + 259 = 2849
Step 12: 2849 + 259 = 3108
Step 13: 3108 + 259 = 3367
Step 14: 3367 + 259 = 3626
Step 15: 3626 + 259 = 3885

So, 259*15 = 3885