Lucy has a total of $20 to spend and she's buying a shirt that costs $8. To find out how much money she has left to spend after buying the shirt, we can set up an inequality.
Let \( x \) be the amount of money Lucy has left to spend. After buying the shirt, the amount of money remaining can be expressed as:
\[ 20 - 8 \geq x \]
This simplifies to:
\[ 12 \geq x \]
or equivalently:
\[ x \leq 12 \]
Therefore, the inequality that can be used to find how much money she has left to spend is:
\[ x \leq 12 \]
This means Lucy can spend up to $12 after buying the shirt.