Which could be first step in solving the equation represented by the model

Add 4 positive unit tiles to each side

Step-by-step explanation:

The tiles represent an algebraic equation. The first step in solving an equation like this is moving all constants to one side. The constants are the numbers with variables or x's. By adding 4 units to both sides all constants are on the right side. All the other choices would leave some constants on both sides.

for the friend request.

when a figure, such as triangle (xyz) is reflected over the line y = x to create x'y'z' the x-coordinates and y-coordinates of the original image (pre-image) will be reversed for the image. (e.g., (x, y) > (y, x)) this means that the pre-image position of the x- and y-coordinates switch places which in turn provides a mirror like image of the original xyz.  

i notice that when i draw a line segment from x to x', that the points are parallel from each other -- they are exactly across from each other and do not intersect with any other points.  

yes, think i would see the same characteristic if you drew the line segment connecting y with the reflecting line and then y' with the reflecting line because of the essence of reflections. because it is a mirror image, each point was effected the same way which leads me to conclude that they same would apply to y and y'.

more i think

hope this !