Question

Solve the equations using elimination method:
$m+n=7$ and $2m-3n=9$

• A. (6, -1)
• B. (-6, 1)
• C. (6, 1)
• D. (-6, -1)

Answer 1

The correct option is C (6, 1)

$m+n=7$ ----- (1)
$2m-3n=9$----- (2)
Multiply equation (1) by 3 and then subtract the equation (3) and (4)
$3m+3n=21$ ----- (3)
$2m-3n=9$ ----- (4)
______________
$5m=30$
$m=\frac{30}{5}=6$
Put the value of m in equation (1), we get
$m+n=7$
$6+n=7$
$n=76$
$n=1$
Therefore the solution is (6, 1)