Answer
So the distance of the congruent sides = 5
Work Step by Step
As we know the diagonals of a rhombus equally divides each other at $90^{\circ}$.
So the distance of the congruent sides is the hypotenuse of the right triangle formed by the diagonals of the rhombus .
The two sides of the triangle are half of the diagonals means 3 and 4.
$Hypotenuse^{2}= 3^{2}+4^{2}$
Hypotenuse = 5
So the distance of the congruent sides = 5.