Example

Example: Solving a Part-Time Job Income Application with a Linear Inequality in Two Variables

To solve a real-world application using a linear inequality in two variables, translate the constraints into an inequality and graph it to find valid combinations.

For example, consider Hilaria, who works at a food service job paying 1010 dollars an hour and a tutoring job paying 1515 dollars an hour. She needs to earn at least 240240 dollars a week. Translate into an inequality: Let xx be the number of food service hours and yy be the number of tutoring hours. The inequality is 10x+15y24010x + 15y \geq 240. Graph the inequality: Convert it to slope-intercept form to find the boundary line: 15y10x+24015y \geq -10x + 240 y23x+16y \geq -\frac{2}{3}x + 16 Graph the solid boundary line (since the symbol is \geq) and shade the corresponding half-plane above it. Find solutions: Any point in the shaded region is a valid solution. For instance, the ordered pairs (15,10)(15, 10), (0,16)(0, 16), and (24,0)(24, 0) fall in the solution area. This means Hilaria could work 1515 hours tutoring and 1010 hours at food service; 1616 hours exclusively tutoring; or 2424 hours exclusively in food service.

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Updated 2026-04-23

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