This is just the answer digitally i cant explain the process
An obtuse triangle is formed if there is an angle that has a measure of more than 90 degrees. You can determine if an obtuse angle is formed by two sides of a triangle if it meet this condition:
Let a and b be two sides of a triangle and c is the longest side:

So taking your given:

<

100 + 225 <

325 <

To get the smallest possible number, just get the square root of both sides:

<

18.03 < c
So your smallest possible whole number is 19
It takes her (100 mi)/(50 mi/h) = 2 h to get to her destination. She has 1 h 40 min = 100 min for her 100 mi return trip.
.. (100 mi)/(100 min) = (60 mi)/(60 min) = 60 mi/h
She must return at the rate of 60 mph to complete the trip in 3 h 40 min.