Respuesta :
7x + 4y = 31
- 7x - 7x
-------------------------
4y = -7x + 31
------ ------ ------
4 4 4
y = -7/4x + 31/4
- 7x - 7x
-------------------------
4y = -7x + 31
------ ------ ------
4 4 4
y = -7/4x + 31/4