Question

I. $8x+7y=135$
II. $5x+6y=99$
III. $9y+8z=121$

• A. $x<y=z$
• B. $x\le y<z$
• C. $x<y>z$
• D. $x=y>z$
• E. $x=y=z$ or none of the above relationship is established

Answer 1

The correct option is D $x=y>z$

By equation $1\times 5-II\times 8$
$40x+35y=67540x+48y=792\underset{–}{---}-13y=-117\Rightarrow y=9$
From equation I,
$8x+7\times 9=135\Rightarrow 8x=135-63=72\Rightarrow x=9$
From equation III,
$9\times 9+8z=121\Rightarrow 8z=121-81=40\Rightarrow z=5$
Clearly, $x=y>5$