5

Set 12: Systems of Equations (Intermediate)

Explanation

Answer: C

Solve by elimination: {2x+5y=243x2y=5\begin{cases} 2x + 5y = 24 \\ 3x - 2y = 5 \end{cases}

A.

(2,4)(2, 4)

B.

(4,3.2)(4, 3.2)

C.

(3,185)(3, \frac{18}{5})

✓ Correct
D.

(5,2.8)(5, 2.8)

Detailed Explanation

Choice C is correct. Choice C is the correct answer. We need to multiply both equations to eliminate a variable. Step 1: Multiply first equation by 2 and second by 5: 4x + 10 y = 48$$15x - 10 y = 25 Step 2: Add the equations: $$$19x = 73x = \frac{73}{19}$$ Non-integer. - First: 2(3) + 5(\frac{18}{5}) = 6 + 18 = 24Second:✓ - Second:3(3) - 2(\frac{18}{5}) = 9 - \frac{36}{5} = \frac{45-36}{5} = \frac{9}{5} \neq 5StrategicTip:Whencoefficientsdontmatch,multiplybothequationstocreateoppositecoefficients.ChoiceAisincorrectbecauseStrategic Tip: When coefficients don't match, multiply both equations to create opposite coefficients. Choice A is incorrect because2(2) + 5(4) = 24,but✓, but3(2) - 2(4) = -2 \neq \frac{9}{5}.ChoiceBisincorrectbecause. Choice B is incorrect because 2(4) + 5(3.2) = 24,butsubstitutioninsecondfails.ChoiceDisincorrectbecause✓, but substitution in second fails. Choice D is incorrect because2(5) + 5(2.8) = 24$ ✓, but substitution in second fails.

Key Steps:

The correct answer is (3,185)(3, \frac{18}{5})

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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