We could start by drawing the triangle we are given. However, it would be better to draw the triangle after the y-axis reflection. To calculate the y-axis reflection, we first think as follows
We see that the reflected point is at the same height as the original point. This means that the y coordinate should remain the same. So, the only thing that changed is the x coordinate. This suggests that, to calculate the reflection about the y-axis, we simply multiply by -1 the first coordinate. So, after the reflection we get the points
P'(-3*(-1),9)=(3,9)
Q'(-3*(-1),5)=(3,5)
R'(-7*(-1),5) =(7,5)
Now, if we plot this points we get
So, if we rotate this 180° we would get the following
So the new points after rotating 180°, would be
P''(-3,-9)
Q''(-3,-5)
R''(-7,-5)
