Choice B is the correct answer. Let $p$ = pounds of peanuts.

Step 1: Set up the equation: $\frac{12(10) + 6p}{10 + p} = 9$

The numerator is total value, denominator is total weight.

Step 2: Multiply both sides by $(10 + p)$: $120 + 6p = 9(10 + p)$$120 + 6p = 90 + 9p$$120 - 90 = 9p - 6p$$30 = 3p$$p = 10$

Solution: 10 pounds of peanuts

Verification:

• Total value: $12(10) + 6(10) = 120 + 60 = 180$
• Total weight: $10 + 10 = 20$
• Price per pound: $\frac{180}{20} = 9$ ✓

💡 Strategic Tip: Mixture problems: (sum of values) ÷ (sum of quantities) = average price.

Choice A is incorrect because $\frac{120 + 48}{18} = \frac{168}{18} \approx 9.33 \ eq 9$.

Choice C is incorrect because $\frac{120 + 72}{22} = \frac{192}{22} \approx 8.73 \ eq 9$.

Choice D is incorrect because $\frac{120 + 90}{25} = \frac{210}{25} = 8.4 \ eq 9$.