Linear inequalities drills

Solve, graph, and write linear inequalities from a described situation, including flipping the sign when multiplying/dividing by a negative.

Free, timed SHSAT practice sets on linear inequalitiesβ€” every question includes a full worked explanation, and there's no account required.

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How to solve linear inequalities

Solve an inequality like an equation, with one extra rule: when you multiply or divide both sides by a negative number, flip the sign.

Example: \(-2x + 10 \le 28\). Subtract \(10\): \(-2x \le 18\). Divide by \(-2\) and flip the sign: \(x \ge -9\). Adding or subtracting never flips the sign.

Words to symbols:

A weekly pay of \(40\) dollars plus \(6\) dollars a sale that must be at least \(130\) dollars is \(40 + 6s \ge 130\).

Whole-number answers: if \(s \ge 12.4\) and \(s\) counts sales, the least answer is \(13\). Round in the direction the sign points, then check the number in the original inequality.

Worked examples

Example 1.
Solve the inequality: \(-4x + 15 β‰₯ 55\).
Show answer and explanation
Answer:
D

Subtract 15: \(-4x β‰₯ 40\). Divide by -4 (negative), flipping the inequality: \(x ≀ -10\). (Forgetting to flip gives \(x β‰₯ -10\). Dividing by -4 first and then subtracting 15 gives \(x ≀ -115/4\). Dividing by 4 instead of -4 gives \(x β‰₯ 10\).)

Example 2.
A salesperson earns \(50\) dollars a day plus \(5\) dollars for each sale \(s\). She wants to earn at least \(100\) dollars in one day. Which inequality shows the number of sales she needs?
Show answer and explanation
Answer:
A

The fixed \(50\) dollars plus \(5\) dollars per sale is the total, \(50 + 5s\). "At least \(100\)" means the total can equal \(100\) or be more, so the symbol is \(\ge\): \(50 + 5s \ge 100\). (\(\le\) points the wrong way: it means at most \(100\). \(>\) leaves out exactly \(100\). \(5 + 50s\) swaps the daily pay and the pay per sale.)

Example 3.
Ana earns \(45\) dollars a day plus \(4\) dollars for each sale. What is the least whole number of sales she needs to earn at least \(120\) dollars in one day?
Show answer and explanation
Answer:
19

Write \(45 + 4s \ge 120\). Subtract \(45\): \(4s \ge 75\). Divide by \(4\): \(s \ge 18.75\). Sales are whole numbers, so round UP: \(19\). (\(18\) sales give only \(117\) dollars.)