Question

x+y=7 and 5x+12y=7 by substitution

Answer 1

Ahoy,


↪x+y=7

=> x = 7-y


↪5x+12y=7

Now, putting the value of x in this equation we get,

=>5(7-y)+12y = 7

=>35-5y+12y=7

=>7y=7-35

=>7y=-28

=>y=-4


Then x=7-y

=>x=7-(-4)
=>x=7+4

=>x=11

Answer 2

Solution :

$x + y = 7 \\ 5x + 12y =7\\\\ Let \ us \ take \ the \ first \ eq. \\ x + y = 7 \\ x = 7 - y \\\\ Putting \ the \ value \ of \ x \ in \ second \ eq. \\ 5x + 12y = 7 \\\ 5 X (7-y) + 12y = 7\\ 35 - 5y + 12y = 7 \\ - 5y + 12y = 7 - 35 \\ \to 7y = -28\\ \to y = \frac{-28}{7} \\ \to y = -4 \\\\ Putting \ the \ value \ of \ y \ in \ equ. first \\ x + y = 7\\ x + (-4) = 7\\ x = 7 - (-4)\\ x = 7 + 4 \\ x = 11$

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