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zvonat [6]
3 years ago
14

Solve y=3x-7 and 4x+3y=18 by substitution

Mathematics
2 answers:
Schach [20]3 years ago
5 0

Answer:

x = 3

y = 2

Step-by-step explanation:

4x + 3(3x - 7) = 18 <em>Substitute</em><em> </em><em>y</em>

4x + 9x - 21 = 18 <em>Simply</em>

13x - 21 = 18 <em>Add</em><em> </em><em>like</em><em> </em><em>terms</em>

13x = 39 <em>Add</em><em> </em><em>2</em><em>1</em>

x = 3 <em>Divide</em><em> </em><em>by</em><em> </em><em>1</em><em>3</em>

y = 3(3) - 7 <em>Substitute</em><em> </em><em>x</em>

y = 9 - 7 <em>Simply</em>

y = 2 <em>Subtract</em>

Let's check:

4(3) + 3(2) = 18

12 + 6 = 18

18 = 18

It works!

Monica [59]3 years ago
5 0

Answer:

\huge\boxed{x=3,\ y=2\to(3,\ 2)}

Step-by-step explanation:

\left\{\begin{array}{ccc}y=3x-7&(1)\\4x+3y=18&(2)\end{array}\right\\\\\text{Substitute (1) to (2):}\\\\4x+3(3x-7)=18\qquad\text{use the distributive property}\\\\4x+(3)(3x)+(3)(-7)=18\\\\4x+9x-21=18\qquad\text{add 21 to both sides}\\\\4x+9x-21+21=18+21\qquad\text{cobine like terms}\\\\13x=39\qquad\text{divide both sides by 13}\\\\\dfrac{13x}{13}=\dfrac{39}{13}\\\\\boxed{x=3}\\\\\text{Substitute it to (1):}\\\\y=3(3)-7\\\\y=9-7\\\\\boxed{y=2}

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