Choice B is the correct answer. Let $x$ = pounds of $2 flour and $y$ = pounds of $5 flour.

System: $\begin{cases} x + y = 60 \\ 2x + 5y = 3.50(60) \end{cases}$

Step 1: Simplify: $\begin{cases} x + y = 60 \\ 2x + 5y = 210 \end{cases}$

Step 2: From first: $y = 60 - x$

Step 3: Substitute: $2x + 5(60 - x) = 210$$2x + 300 - 5x = 210$$-3x = -90$$x = 30$

Solution: 30 pounds of $2 flour (and 30 pounds of $5 flour)

Verification: $2(30) + 5(30) = 60 + 150 = 210$ ✓ and $\frac{210}{60} = 3.50$ ✓

💡 Strategic Tip: The mixture's total value = sum of individual values.

Choice A is incorrect because $2(25) + 5(35) = 50 + 175 = 225 \ eq 210$.

Choice C is incorrect because $2(35) + 5(25) = 70 + 125 = 195 \ eq 210$.

Choice D is incorrect because $2(40) + 5(20) = 80 + 100 = 180 \ eq 210$.