OK, let's work through this together. We're starting with 905 and we're going to multiply it by 13, which means we add 905 to itself 13 times.
Step 1: 0 + 905 = 905
Step 2: 905 + 905 = 1810
Step 3: 1810 + 905 = 2715
Step 4: 2715 + 905 = 3620
Step 5: 3620 + 905 = 4525
Step 6: 4525 + 905 = 5430
Step 7: 5430 + 905 = 6335
Step 8: 6335 + 905 = 7240
Step 9: 7240 + 905 = 8145
Step 10: 8145 + 905 = 9050
Step 11: 9050 + 905 = 9955
Step 12: 9955 + 905 = 10860
Step 13: 10860 + 905 = 11765

So, 905*13 = 11765