Hey there! I'm happy to help!
A line of symmetry is a line that cuts a figure in half so that it is the same on both sides. We cannot do a vertical line because one side is different than another. We could do a horizontal line where y=3 the whole time. This would cut the shape in half so it is the same on both sides.
Therefore, the equation for the line of symmetry in this figure is y=3.
Have a wonderful day! :D
