Since P is transformed to P' by a glide reflection consisting of a translation and a reflection, we can first apply the translation to P and then reflect the result about the line x=0 to get P'.
Let P = (x, y) be the coordinates of P. Then the translation of P is given by:
P1 = (x, y + 3)
To reflect P1 about the line x=0, we negate the x-coordinate of P1, giving:
P' = (-x, y + 3)
We know that P' has coordinates (4, 2), so we can set the x and y values equal to 4 and 2 respectively, and solve for x and y:
x = 4, so x = -4
y + 3 = 2, so y = -1
Therefore, the coordinates of P are (x, y) = (-4, -1)