First plot the points so you know what you're working with. The choose a side and use the pythagorean theorem to find the length. Do this to corresponding side of bot triangles (I'll use the shortest sides). Remember a² + b² = c². The shortest side of PQR is √8 and the shortest side of P'Q'R' is √32. Divide √8 by √32 to find the scale factor. √8 ÷ √32 = 1/2. This means that PQR was dilated by 1/2 to get P'Q'R'. If triangle P'Q'R' is reflected across the x axis, the x values will flip and the y values will stay the same. The coordinates will be (1,-2) (-3,1) and (-4,0). (I tried to draw it as the purple triangle but it got cut off a little). P'Q'R' and P"Q"R" are congruent because the reflection preserves the side lengths - only a dilation will change congruency.
I hope this helps!
