3

Set 2: Systems of Equations (Advanced)

Explanation

Answer: C

Solve: {2x+3y=172x3y=7\begin{cases} 2x + 3y = 17 \\ 2x - 3y = 7 \end{cases}

A.

(5,73)(5, \frac{7}{3})

B.

(7,1)(7, 1)

C.

(6,53)(6, \frac{5}{3})

✓ Correct
D.

(4,3)(4, 3)

Detailed Explanation

Choice C is correct. Choice C is the correct answer. The 3y3y terms are opposites, so we add the equations. Step 1: Add the equations: (2 x + 3 y) + (2 x - 3 y) = 17 + 7$4x = 24$x = 6 Step 2: Substitute x=6x = 6 into the first equation: 2(6) + 3 y = 17$12+ 3 y = 173y = 5y = \frac{5}{3}$$ Solution: (6, \frac{5}{3})Verification:Verification:2(6) - 3(\frac{5}{3}) = 12 - 5 = 7StrategicTip:DontbeafraidoffractionalanswerstheyrecommonontheSAT.ChoiceAisincorrectbecause✓ Strategic Tip: Don't be afraid of fractional answers—they're common on the SAT. Choice A is incorrect because2(5) + 3(\frac{7}{3}) = 10 + 7 = 17,but✓, but2(5) - 3(\frac{7}{3}) = 10 - 7 = 3 \neq 7.ChoiceBisincorrectbecause. Choice B is incorrect because 2(7) + 3(1) = 14 + 3 = 17,but✓, but2(7) - 3(1) = 14 - 3 = 11 \neq 7.ChoiceDisincorrectbecause. Choice D is incorrect because 2(4) + 3(3) = 8 + 9 = 17,but✓, but2(4) - 3(3) = 8 - 9 = -1 \neq 7$.

Key Steps:

The correct answer is (6,53)(6, \frac{5}{3})

Why others are wrong:
A: Choice A is incorrect and may result from a calculation error.
B: Choice B is incorrect and may result from a calculation error.
D: Choice D is incorrect and may result from a calculation error.

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