Which of the following is a linear equation in two variables?
 
(i) \((x+1) + (y+3) = 2(x+3) - (2y+5)\)  \(=\)
 
(ii) \((x+4) + (2y+3) = 2(2x+3) - (2y+5)\) \(=\)  
 
(iii) \(3x^2 + 5x =3x^2 + 2(y + 2)\) \(=\)