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3 years ago

If 7x - 4y = 23 and x + y = 8, what is the value of x?

Mathematics

2 answers:

Margaret [11]3 years ago

8 0

Answer:

x=5

Step-by-step explanation:

7x - 4y = 23 and x + y = 8

Multiply the second equation by 4

4x + 4y = 32

Add this to the first equation

7x - 4y = 23

4x + 4y = 32

------------------------

11x = 55

Divide each side by 11

11x/11 = 55/11

x = 5

QveST [7]3 years ago

5 0

Answer:

$\huge\boxed{x=5}$

Step-by-step explanation:

$\left\{\begin{array}{ccc}7x-4y=23\\x+y=8&|\text{subtract}\ x\ \text{from both sides}\end{array}\right\\\left\{\begin{array}{ccc}7x-4y=23&(1)\\y=8-x&(2)\end{array}\right\\\\\text{substitute (2) to (1):}\\\\7x-4(8-x)=23\qquad|\text{use the distributive property}\\\\7x+(-4)(8)+(-4)(-x)=23\\\\7x-32+4x=23\qquad|\text{combine like terms}\\\\(7x+4x)-32=23\qquad|\text{add 32 to both sides}\\\\11x-32+32=23+32\\\\11x=55\qquad|\text{divide both sides by 11}\\\\\dfrac{11x}{11}=\dfrac{55}{11}\\\\x=5$

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