If the polygons are similar, then the top side is equal to one half of the left side.
Since side (x -1) = 8, then x = 9.
Combine numbers with the same variable so 10a + 7a = 17a and 3b + 6b = 9b. So the full answer is 17a + 9b.
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.