Hi there!
The perimeter is when you add all the sides of a shape. In a rectangle, two sides are the same, and so are the other two. So, if the two sides are 2x-3 and x+2 the expression will be:
2(2x-3) + 2(x+2)
If we were to simplify this, it would be
4x-6+2x+4
6x-2
Hope this helps!