Set 5: Systems of Equations (Intermediate)

Choice B is correct. Choice B is the correct answer. Let $x$ = liters of 25% solution to add. Equation: (amount of salt) before mixing = (amount of salt) after mixing $0.10(20) + 0.25 x = 0.18(20 + x)$ Step 1: Expand: $2+ 0.25 x = 3.6 + 0.18 x$ Step 2: Solve: $$$0.25x - 0.18 x = 3.6 - 20.07x = 1.6$x = \frac{1.6}{0.07} = \frac{160}{7} \approx 22.86$0.10(20) + 0.25(20) = 2 + 5 = 7$ total salt Total solution: 20+ 20 = 40liters Concentration: $\frac{7}{40} = 0.175 = 17.5\%$ ✗2+ 0.25 x = 0.18(20 + x)2+ 0.25 x = 3.6 + 0.18 x0.07x = 1.6$x = 22.857...$ Strategic Tip: Mixture problems: concentration × volume = amount of substance. Other choices based on calculation.