Let's get this math done. We have 378 and we're going to multiply it by 7. This is the same as taking 378 and adding it to itself 7 times.
Step 1: 0 + 378 = 378
Step 2: 378 + 378 = 756
Step 3: 756 + 378 = 1134
Step 4: 1134 + 378 = 1512
Step 5: 1512 + 378 = 1890
Step 6: 1890 + 378 = 2268
Step 7: 2268 + 378 = 2646

So, 378*7 = 2646