Concept:
Area of a rhombus:
\[
A=\frac12 d_1d_2
\]
where \(d_1,d_2\) are diagonals.
Also, diagonals bisect each other at right angles.
Step 1: Find the second diagonal.
Given:
\[
A=24
\]
\[
d_1=8
\]
So:
\[
24=\frac12(8)(d_2)
\]
\[
24=4d_2
\]
\[
d_2=6
\]
Step 2: Use half diagonals to form a right triangle.
Half diagonals:
\[
\frac{8}{2}=4
\]
\[
\frac{6}{2}=3
\]
Side of rhombus:
\[
=\sqrt{4^2+3^2}
\]
\[
=\sqrt{16+9}
\]
\[
=\sqrt{25}
\]
\[
=5
\]
Thus, the side of the rhombus is:
\[
\boxed{5}
\]