Choice C is the correct answer. The $y$ terms are opposites ($+y$ and $-y$), so we can add the equations to eliminate $y$.

Step 1: Add the two equations: $(3x + y) + (3x - y) = 13 + 5$$6x = 18$$x = 3$

Step 2: Substitute $x = 3$ into the first equation: $3(3) + y = 13$$9 + y = 13$$y = 4$

Solution: $(3, 4)$

Verification: $3(3) - 4 = 9 - 4 = 5$ ✓

💡 Strategic Tip: When coefficients are opposites, adding eliminates that variable immediately.

Choice A is incorrect because$3(2) + 7 = 6 + 7 = 13$ ✓, but $3(2) - 7 = 6 - 7 = -1 \ eq 5$.

Choice B is incorrect because$3(4) - 1 = 12 - 1 = 11 \ eq 5$.

Choice D is incorrect because$3(5) - (-2) = 15 + 2 = 17 \ eq 5$.