Verified Answer :

TSO

This is an example of the commutative property of multiplication.

That property states: \((a \times b) \times c = a \times (b \times c)\)

So using that property, we can figure out that 3 should be in the blank.

Leader

Using the property \((a\times b) \times c = a \times (b\times c)\), we know that 3 is the missing number.