Question

Solve 9x - 4y = 8 & 13x + 7y = 101

• A. $x=7,y=3$
• B. $x=9,y=3$
• C. $x=1,y=3$
• D. $x=4,y=7$

Answer 1

The correct option is D $x=4,y=7$

$9x-4y=8$ -------- (i)
$13x+7y=101$ --------(ii)
Multiplying equation (i) by $7$ and (ii) by $4$ and subtracting we get,
$63x-28y=56$ --------(iii)
$52x-28y=404$ --------(iv)

$115x=460$
$x=\frac{460}{115}$
$x=4$
Putting the value of $x$ in (i) we get,
$9\left(4\right)-4y=8$
$\to 36-4y=8$
$\to -4y=8-36$
$\to -4y=-28$
$\to y=\frac{28}{4}$
$\to y=7$