Choice A is the correct answer. Let $a$ = pounds of apples and $o$ = pounds of oranges.

System: $\begin{cases} a + o = 12 \\ 1.5a + 2o = 21 \end{cases}$

Step 1: From first: $o = 12 - a$

Step 2: Substitute: $1.5a + 2(12 - a) = 21$$1.5a + 24 - 2a = 21$$-0.5a = -3$$a = 6$

Solution: 6 pounds of apples

Verification: $6 + 6 = 12$ ✓ and $1.5(6) + 2(6) = 9 + 12 = 21$ ✓

💡 Strategic Tip: Decimal coefficients can be eliminated by multiplying, but substitution works fine too.

**Other choices fail verification.