First find least common denominator to subtract.
9=(3)×3
15=(3)×5
3×3×5=45 is lcd
4/9=20/45
7/15=21/45
(20/45-21/45)=(20-21)/45=-1/45
-1/45÷13/10
multiply by reciprocal instead of dividing
-1/45×10/13=(1×10)/(45×13)
-10/585
Answer: Interval = [103,∞)
Explanation :
A medicine become ineffective if its temperature ever reaches 103 degrees Fahrenheit or more .
So, Interval becomes [103,∞)
i.e. semi-open or semi-closed interval as it includes 
So, we used closed brackets i.e. square brackets and
For '∞' we always use open brackets only.
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