What Is a Literal Equation?

We know addition is commutative, meaning that the values being added together can change their order without changing the overall result; symbolically, this can be represented with $a + b = b + a$.

Keeping that in mind, we immediately see that in the equation $$13+20 = 20+x,$$ $x=13$.

What about the following equation?

$$13 + y = 20 + x$$