Will mark brainliest plz help !

4
Explaining:
AE = AD = BD = 2+3=5
By the Pythagoras’s rule
The sum of squares of legs equals to the square of hypotenuse. And one of the legs(CD) Equals to the Root of residual of the squares of leg and hypotenuse.
CD = BC = root of 5^2 - 3^2 = 5-3=2
And BD = 2*2=4