The correct answer is:
We can use the associative property to write 70 as 710. We can do this same process to write 6000 as 61000. This gives us:
(710)(61000)
Using the commutative property, we can rearrange the factors of this problem
(76)(101000)
76 is in our multiplication tables, and we know that powers of 10 allow us to just add the correct number of zeros. This means we would have 76=42, and have 4 zeros, for 420000.