The Distributive Property of Multiplication

Let $a$, $b$ represent members of $\mathbb{W}$ or $\mathbb{Z}$ then:

$$ a \cdot (b + c) = a \cdot b + a \cdot c $$

When faced with $4(2\cdot3)$ we may proceed with the official order of operations in algebra, namely:

4 x (2 + 3) = 4 x (5)
= 20

In other words we find the sum of the values in parentheses and then multiply this by the value outside of the brackets.

When we use distributive property we distribute each value in the parentheses against the value outside of the parentheses:

4 x (2 + 3) = (4 x 2) + (4 x 3)
8 + 12 = 20