x + y = 4 .....(I)
2x - 5y = 1 .....(II)
From (I) we have
x = 4 - y
Putting this value of x in (II)
2 ( 4 - y ) - 5y = 1
⇒ 8 - 2y - 5y = 1
⇒ 8 - 7y = 1
⇒ 8 - 1 = 7y
⇒ 7 = 7y
⇒ y = 1.
Putting the value of y in (I) we have
x + 1 = 4
⇒ x = 3
Thus, ( x , y ) = ( 3,1 )