Choice A is the correct answer. Isolate $y$ from the first equation.

Step 1: From $2x + y = 15$: $y = 15 - 2x$

Step 2: Substitute into the second equation: $3x - 4(15 - 2x) = 6$$3x - 60 + 8x = 6$$11x = 66$$x = 6$

Step 3: Find $y$: $y = 15 - 2(6) = 3$

Solution: $(6, 3)$

Verification: $3(6) - 4(3) = 18 - 12 = 6$ ✓

💡 Strategic Tip: Isolating $y$ was natural since its coefficient in the first equation is 1.

Choice B is incorrect because$3(4) - 4(7) = 12 - 28 = -16 \ eq 6$.

Choice C is incorrect because$3(5) - 4(5) = 15 - 20 = -5 \ eq 6$.

Choice D is incorrect because$3(7) - 4(1) = 21 - 4 = 17 \ eq 6$.