Graph the image of the given triangle after the transformation with the rule ( x, y ) --> ( x, -y ).

The transformation rule (x,y) ---> (x,-y) tells us that the x coordinate stays the same while the y coordinate will flip from positive to negative (or vice versa)

A point like (x,y) = (2,3) becomes (x,-y) = (2, -3)

Something like (x,y) = (7,4) will turn into (x,-y) = (7,-4)

Finally the point (x,y) = (6,8) reflects onto (x,-y) = (6,-8)

The three points that make up the final answer are: (2,-3) and (7,-4) and (6,-8)

The reflection that happened is a reflection over the horizontal x axis.