This is the answer because like terms are alike. For example: With 2x and 5x what do they have in common? They have the x in common. Another example is if you have (2 + 7 + 5x + 10y). What are the like terms? 2 and 7, because they are both integers. Also, if you are trying to solve an expression such as the last example, then you would add 2 + 7, because they are similar, so they can be added. So it would be (9 + 5x + 10y).
The commutative property can be used because 70 • 6000 is the same as 6000 • 70.
Mark can calculate the product mentally by taking off all the zeros to get 7 • 6 which is 42. After, he can add the zeros back on. The answer is 420,000.
