The vertices of a triangle are p(-4,1), q(-2,-8), and r(8,-1). what are the vertices of the image reflected across the y-axis?

An image reflected over the x axis is in the same position on the x axis, but the opposite position on the y axis. So if you had a line at (2,2) to (4,5) and you reflected it over the x axis it would be at (2,-2) to (4, -5) 

Now apply this to our problem..

P(-4, 1) > P(-4, -1)
Q(-2, -8) > Q(-2, 8)
R(8, -1) > R(8, 1)

Hope this helps!