if -2x+9y=7 and -3x-2y=-5, what is x+y

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Given -2x+9y=7 --- (i)

and -3x-2y=-5 --- (ii)

For eliminating x, multiply eqn.(i) with 3 and eqn.(ii) with 2, to get

      -6x+27y=21
and -6x-4y=-10

Now subtract,

 -6x+27y=21
 -6x-4y=-10

--------------------

0+31y=31

rArr y=31/31=1

Put this value of y in eq. (i)

-2x+9*1=7

rArr -2x=7-9=-2

rArr x=-2/-2=1

Therefore, x+y=(1+1)=2

 

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