Help yourself and potential helpers by getting started and sharing all the work you've done, please.
In Problem 19, it surely sounds as tho' reflection in the y-axis is taking place. The y-coordinate remains the same, but the x-coordinate changes sign.
Suppose that the point you've invented is (2, -5). Rewrite this, leaving the '2' as is, but changing the sign of that "-5." What's your new point?
Plot (2, -5) and (-2, -5). Do these points satisfy the specifications given in this problem?