Answer :
9x8 is equal to (9x4)x2. In other words, 9x8 is twice as much as 9x4. So if you know the answer to 9x4 (36), you can just double it and get the answer to 9x8 (72).
In multiplication, we can apply the commutative property, this means that:
abc = acb
Now, we know that:
8 = 4 * 2
This means that:
9*8 = 9 * 4 * 2
This means that
9*8 is twice as much as 9*4 is 36, we can simply multiply this value by 2 to get 9*8
Therefore:
9 * 8 = 2 (9*4) = 2(36) = 72
Hope this helps :)
