Question

Match the correct value of y in the below equations if x = 3

• A. 8
• B. 0.0
• C. 1
• D. 2

Answer 1

$\text{Case(1):}$
$2x+y=7$
$\because x=3$
$\therefore 2\times 3+y=7$
$6+y=7$
$6-6+y=7-6$
$y=1$

$\text{Case(2):}$
$x+y=3$
$\because x=3$
$\therefore 3+y=3$
$3-3+y=3-3$
$y=0$

$\text{Case(3):}$
​​​​​​​$x+2y=7$
$\because x=3$
$\therefore 3+2\times y=7$
$3-3+2\times y=7-3$
$2\times y=4$
$y=\frac{4}{2}$
$y=2$

$\text{Case(4):}$
​​​​​​​$3x-y=1$
$\because x=3$
$\therefore 3\times 3-y=1$
$9-y=1$
$9-y+y=1+y$
$9=1+y$
$9-1=1+y-1$
$y=8$