The Commutative property: Addition only

In order to simplify our calculations, we try to add numbers that give us a round result.

Keep in mind that:

$19+21=40$

$34+6=40$

Now, we get a more manageable exercise to solve:

$40+40+10=80+10=90$

In order to simplify the resolution process we try to add numbers that give us a round result.

Keep in mind that:

$4+4=8$

Now we get the exercise:

$74+36+6+8=$

Keep in mind that:

$74+6=80$

$32+8=40$

Now, we get a more manageable exercise to solve:

$80+40=120$

To make solving the exercise easier, we try to add numbers that give us a result of 10.

Let's keep in mind that:

$7+3=10$

$6+4=10$

Hence we obtain a more manageable exercise to solve:

$10+10=20$

In order to simplify our calculations we try to add numbers that give us a round result.

Let's keep in mind that:

$113+57=170$

$59+71=130$

Now we have a more manageable exercise to solve:

$170+130=300$