Question

If 8x -7y =11 and 7x-8y =4 , then what is the value of x + y *

1 point

A ) 1

B ) -1

C ) 7

D ) -7​

Answer 1

$\large\underline{\sf{Given- }}$

A pair of linear equations

8x - 7y = 11

7x - 8y = 4

$\large\underline{\sf{To\:Find - }}$

The value of x + y.

$\large\underline{\sf{Solution-}}$

The given pair of linear equations are

$\rm :\longmapsto\:8x - 7y = 11 - - - (1)$

$\rm :\longmapsto\:7x - 8y = 4 - - - (2)$

On Subtracting equation (2) from equation (1), we get

$\rm :\longmapsto\:8x - 7y - (7x - 8y) = 11 - 4$

$\rm :\longmapsto\:8x - 7y - 7x + 8y = 7$

$\rm :\implies\:x + y = 7$

$\boxed{ \sf \:Option \: (C) \: is \: correct}$

$\large\boxed{ \sf \: Additional \: Information}$

There are 4 methods to solve the pair of linear equations.

• 1. Method of Substitution

• 2. Method of Eliminations

• 3. Method of Cross Multiplication

• 4. Graphical Method