To rotate a point \((x, y)\) counterclockwise by 270 degrees about the origin, you can use the following transformation formula:
\[ (x, y) \rightarrow (y, -x) \]
Starting with the point \((5, 8)\):
- \(x = 5\)
- \(y = 8\)
Applying the transformation:
\[ (5, 8) \rightarrow (8, -5) \]
Thus, the new point after rotating \((5, 8)\) 270 degrees counterclockwise about the origin is \((8, -5)\).
So the correct answer is:
\((8, -5)\)