8 + 5 = 13
10 + 3 = 13
i think thats what you asking right
Since you do not want the variable y, you must eliminate 
Therefore, to eliminate it, you must have the opposite of it, making the answer 
The image that shows the reflection of DFEG over the x-axis is the FIRST option. The x-axis is the mirror line. The distance from the mirror line to the reflected shape equals to the distance from the original image to the mirror line.