## Geometry: Common Core (15th Edition)

By the definition of midpoint, $AD\cong DB$ Substitute the given values. $x+8=2x+5$ Subtract x from each side and simplify. $x+8-x=2x+5-x$ $8=x+5$ Subtract 5 from each side and simplify. $8-5=x+5-5$ $3=x$