OK, let's crack this. We're given 915 and our task is to multiply it by 4. Essentially, we'll be adding 915 to itself 4 times.
Step 1: 0 + 915 = 915
Step 2: 915 + 915 = 1830
Step 3: 1830 + 915 = 2745
Step 4: 2745 + 915 = 3660

So, 915*4 = 3660