Question

For 4x + 5y = 10 and 5x + 4y = 17 , x + y = ? *

1) 27
2) 3
3) 9
4) - 3​

Answer 1

4x + 5y = 10 ........(i)

5x + 4y= 17............(ii)

(i)×5 and (ii)×4

20x + 25y = 50

20x + 16y = 68

- - -

______________

9y = -18,y=-2

and x={10-5×(-2)}÷4

= 5

x+y=5+(-2)

=3(ans)