SAT · Heart of Algebra · Linear inequalities and systems of inequalities
Question sat-q-00047
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The question
A student has a budget of $26. Each notebook costs $7 and a backpack costs $18. If she buys exactly one backpack and x notebooks, what is the maximum value of x she can afford?
- 1
- 8
- 0
- 2
Show answer & worked solution
Answer: 1
Worked solution. Set up the inequality 7x + 18 ≤ 26. Subtract 18: 7x ≤ 8. Divide by 7: x ≤ 1.14. The maximum integer x is 1.
Why each wrong choice is wrong. Off-by-one distractors catch students who solve correctly but round up instead of taking the floor. The fourth distractor is the leftover dollars after the backpack — it ignores the per-notebook division.
Test-day tactic. Whenever a real-world inequality has an integer answer, take the floor — buying 7.4 notebooks doesn't make sense.
About this question type
A linear inequality is solved like a linear equation, except multiplying or dividing both sides by a negative reverses the inequality. Systems of linear inequalities define a feasible region in the plane; the SAT often asks which (x, y) point satisfies all inequalities, or for the maximum value of a linear expression on a feasible region (introductory linear programming, without using that name).
You will see a question shaped like this one on roughly every other official SAT form, typically at a moderate position in the section — solidly within the range that separates a 600-band student from a 700-band student. Treat any miss in this subtopic as a signal to drill the subtopic page before you do another full practice test.
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