To find the minimum score the student needs on the fifth exam to have an average of at least 70%, we can set up an inequality.

Let the score on the fifth exam be represented by $x$.

1. The average of the five exams must be at least 70%, so we have:

   $\frac{65 + 72 + 68 + 75 + x}{5} \geq 70$

2. Simplify by multiplying both sides by 5:

   $65 + 72 + 68 + 75 + x \geq 350$

3. Add up the scores from the first four exams:

   $280 + x \geq 350$

4. Subtract 280 from both sides:

   $x \geq 70$

So, the student must score at least 70 on the fifth exam to achieve an average of 70% or more.

Would you like more details on solving inequalities, or have any questions?

Here are five related questions for further exploration:

1. What if the student wanted an average of 75% instead of 70%?
2. How would the result change if the scores were slightly higher or lower?
3. What is the highest average the student could achieve with a fifth score of 100%?
4. How do we calculate weighted averages if one test is worth more?
5. How would the inequality look if the average requirement was less than 70%?

Tip: When solving inequalities, remember to reverse the inequality sign if you multiply or divide by a negative number.