Answer: The other half of the co-ordinate is 2.
Step-by-step explanation: Let, 'b' be the other half of the co-ordinate (?, -3) that lies on the given straight line as follows:
So, we can say that the point (b, -3) lies on the line (i). That is, the point (b, -3) will satisfy equation (i).
Substituting (x, y) = (b, -3) in equation (i), we get

Therefore, the value of 'b' is 2.
Thus, the other half of the co-ordinate is 2. And the complete co-ordiantes are (2, -3).