Answer:
The correct option is 3.
Explanation:
It is given that two linear graphs intersect at (1,2). It means the solution of both lines is x=1 and y=2.
The equation which is satisfied by x=1 will be the required equation.
In option (1),

Substitute x=1.


Option 1 is incorrect.
In option (2),

Substitute x=1.


Option 2 is incorrect.
In option (3),

Substitute x=1.


Option 3 is correct.
In option (1),

Substitute x=1.


Option 4 is incorrect.
Therefore the correct option is 3.