In triangle ABD, since BE is perpendicular bisector of segment AD =>angle ABE=angle DBE
And angle AEB=angle DEB=90
And,AE=ED ( BE is the perpendicular bisector)
Therefore ,triangle AEB congruent to triangle DEB by (AAS criterion rule)
So, 2x+4=x +7
=>2x-x =7-4
=>x =3
Hope this helps u......!!