Let \( x \) be the number of weeks Sarah works at her part-time job. She currently has $80 and earns $30 each week, so after \( x \) weeks, her total amount of money will be:
\[ 80 + 30x \]
Since she wants to buy a bicycle that costs at least $200, we can set up the following inequality:
\[ 80 + 30x \geq 200 \]
Now, we will solve the inequality for \( x \):
- Subtract 80 from both sides:
\[ 30x \geq 200 - 80 \] \[ 30x \geq 120 \]
- Divide both sides by 30:
\[ x \geq \frac{120}{30} \] \[ x \geq 4 \]
Thus, the solution to the inequality is:
\[ 30x + 80 \geq 200 \]
or expressed in terms of \( x \):
\[ x \geq 4 \]
This means Sarah needs to work at least 4 weeks to afford the bicycle.