The answer depends on the point you are dilating from. Let's assume that it's the origin. Point X will have coordinates such as (-2,4). Dilating by 1/2 means to multiply those coordinates by 1/2, so X' will be at (-1,2). Do the same for the other coordinates.
If you are dilating from another point, measure the x and y distance to each point from the dilation point, then cut those distance in half. For example, if you are dilating from point P at (2,2), then point X, normally at (-2,4), would be 4 units to the left of P along the x-axis and 2 units up from P along the y-axis. X' will be 2 units to the left of P and 1 unit up from P, which puts it at (0,3).
