The Commutative Property of Addition states that the order in which numbers are added does not change the sum. However, your expression \( a^{20} \cdot x^3 \) involves multiplication rather than addition.
If you meant to express a scenario where you want to apply the properties of addition or if you want to rewrite this expression in another form, please clarify. Otherwise, if we were to rewrite \( a^{20} \cdot x^3 \) using the commutative property of multiplication (which does apply here), you could simply rearrange the factors:
\[ x^3 \cdot a^{20} \]
But remember, this is the Commutative Property of Multiplication, not Addition. If you meant to include an addition operation or if you need further assistance, please provide more details!