Question

If $5x+7y-6z+8=19,3x+4y+8z+5=35$ and $6x+3y+12z=22$ the find the value of $x+y+z-74$.

• A. $-69$
• B. $69$
• C. $-59$
• D. $59$

Answer 1

The correct option is A $-69$

Given:
$5x+7y-6z+8=19,3x+4y+8z+5=35$ and $6x+3y+12z-7=22$
Calculation:
$5x+7y-6z+8=195x+7y-6z=11----\left(1\right)$
$\Rightarrow$ $3x+4y+8z+5=35$
$3x+4y+8z=30----\left(2\right)$
$6x+3y+12z-7=22$
$6x+3y+12z=29----\left(3\right)$
Adding equations $1.2$ and $3$ we get,
$14x+14y+14z=70$
$x+y+z=5$
$\Rightarrow x+y+z-74$
$\Rightarrow 5-74=-69$
Required value is $-69$