Question

Solve the following pair of linear (simultaneous) equations by the method of elimination :

$x+y=7$
$5x+12y=7$

• A. $x=11$ and $y=-4$
• B. $x=1$ and $y=7$
• C. $x=13$ and $y=6$
• D. $x=1$ and $y=-3$

Answer 1

The correct option is A $x=11$ and $y=-4$

$x+y=7$ .... (1)

$5x+12y=7$ ....(2)

Multiply eq. (1) by 5, we get

$5x+5y=35$ ....(3)

Subtracting eq(2) from eq.(3)

$5x+5y=35$

$5x+12y=7$

$-$ $-$ $-$

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

$-7y=28$

$y=-4$

Substituting value of $y$ in eq,(1), we get,

$x-4=7$

$x=11$