Choice C is the correct answer. Let $x$ = pounds of $9 tea.

Equation: $\frac{6(12) + 9x}{12 + x} = 7$

Step 1: Multiply both sides by $(12 + x)$: $72 + 9x = 7(12 + x)$$72 + 9x = 84 + 7x$$2x = 12$$x = 6$

Solution: 6 pounds

Verification: $\frac{6(12) + 9(6)}{12 + 6} = \frac{72 + 54}{18} = \frac{126}{18} = 7$ ✓

💡 Strategic Tip: Weighted average = total value ÷ total weight.