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kumpel [21]
3 years ago
12

Solve the system of equations. -4x+7y = 20 & y=3x+15

Mathematics
1 answer:
andreyandreev [35.5K]3 years ago
7 0

Substitute y = 3x + 15 to the equation -4x + 7y = 20:

-4x + 7(3x + 15) = 20          <em>use distributive property</em>

-4x + (7)(3x) + (7)(15) = 20

-4x + 21x + 105 = 20     <em>subtract 105 from both sides</em>

17x = -85     <em>divide both sides by 17</em>

x = -5

Substitute the value of x to the equation y = 3x + 15:

y = 3(-5) + 15

y = -15 + 15

y = 0

<h3>Answer: x = -5 and y = 0</h3>
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3) David goes into a candy store with $5.00. He buys 9 peppermints for $0.15
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<h3>Write an equation that will match the story problem​</h3>

x=(5 - (9 \times 0.15) ) \div 0.25

<em><u>Solution:</u></em>

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David goes into a candy store with $5.00

Total amount with David = $ 5

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And some sour candies. each sour candy costs $0.25

The equation is:

Let the number of sour candies bought be "x"

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3.65 = 0.25 \times x

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<em><u>Thus the equation that will match the story problem​ is:</u></em>

x=(5 - (9 \times 0.15) ) \div 0.25

Where, "x" means number of sour candies bought

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