Answer:
(0, ∞)
Explanation:
A good place to start is by visualizing what the graph looks like on a number line.
For x > 0, it is an open circle at x=0, and shading to the right extending to infinity.
__
So, the left end of the interval is 0, but 0 is not included in the interval.
The right end of the interval is infinity, but there is no such number, so "infinity" is not included in the interval.
"Not included" means you use round brackets ( ) for the corresponding end of the interval. ("Included" would mean you use square brackets [ ].)
So, the interval 0 < x < ∞ is written in interval notation as ...
(0, ∞)