How do you find the coordinates of A in a straight line function​

You did not specify that this is a straight line, so I assume it is not. You must know the function for the line and solve that function for y = f(x) or x = g(y). Then if you know x, use f(x) to get the y coordinate, or if you know y, use g(y) to get the x coordinate.

Iam guessing c. or d.