Question

Veda solves the following system of linear equations by elimination. What is the value of x of the solution?

A –20
B –1
C 1
D 20

Answer 1

To find the value of x, we must arrange first the two equations. We will have:

  4x – 2y = 0     eq. 1

10x + 7y = -3   eq. 2

Eliminate y by multiplying 7/2 to eq. 1

  7/2 {4x – 2y = 0} 7/2

14x – 7y = 0

10x + 7y = -3        ⇒ add eq. 1 to eq. 2

24x = -3

x = -1/8        answer 

Answer 2

we have

$6+4x-2y=0$ -----> equation A

$-3-7y=10x$ -----> equation B  

Multiply equation A by $-3.5$ both sides

$-3.5(6+4x-2y)=-3.5*0$

$-21-14x+7y=0$ ------> equation C

Adds equation C and equation B

$-21-14x+7y=0 \\-3-7y=10x\\ ---------\\-21-14x+7y-3-7y=10x$

$-24-14x=10x\\ 14x+10x=-24\\ 24x=-24\\x=-1$

therefore

the answer is the option B

$x=-1$