Answer:
Reflect across the line y = x (x, y) -> (y, x)
Explanation:
The simplest way is just one step, a reflection across the line y=x. when doing this the rule is (x, y) -> (y, x).
There are a number of ways to do it otherwise, such as a reflection across the x axis then the y axis, or the other way around, or a translaton then reflection. Like I said though, the reflection across y=x is the fastest. Let me know if you have any further questions.