Answer
Subtraction is not commutative because $a-b \ne b-a$.
Refer to the step-by-step part below for the example.
Work Step by Step
Subtraction is not commutative because $a-b$ is usually not equal to $b-a$.
To illustrate this, let us take $a=3$ and $b=1$:
$a-b = 3-1 = 2$
$b-a = 1-3 = -2$
Note that $a-b \ne b-a$.
Thus, subtraction is not commutative.
