You have $20 to spend on taxi fare. The ride costs $5 plus $2.50 per kilometer. Write the inequality

You have $20 to spend on taxi fare. The ride costs $5 plus $2.50 per kilometer. Write the inequality.

Let k be the number of kilometers. We want our total to be $20 or less. We have the following inequality:
2.50k + 5 <= 20