If 7x + 9y = 42 and 9x + 7y = 22, then find the value of x + y

2

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Solution

The correct option is C $4$
$7 x + 9 y = 42$ ...........(1)
$9 x + 7 y = 22$ ...........(2)

Add equations (1) and (2),

$7 x + 9 y + 9 x + 7 y = 42 + 22$

$16 x + 16 y = 64$

$16 (x + y) = 64$

$x + y = 4$

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