The expression Joelle should use to find the tip amount is 38(0.20).
<h2>Expression
</h2>
In mathematics, an expression is defined as a set of numbers, variables, and mathematical operations that are formed according to rules which are dependent on the context.
<h2>Given to us</h2>
Percentage tip of Joelle hairdresser = 20%,
Joelle's haircut costs = $38,
<h3>Percentage Conversion</h3>
As we know that percentage shows a part of something, therefore,

Hence, the expression Joelle should use to find the tip amount is 38(0.20).
Learn more about expression:
brainly.com/question/13947055