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Let x be the smaller dimension, in meters (the width).
Then the larger dimension (the length) is (x+15) meters, according to the condition.
They want you determine x in a way to satisfy inequality
x*(x+15) < 100.
It is equivalent to
x^2 + 15x - 100 < 0,
or, in factored form
(x+20)*(x-5) < 0.
The solution to this inequality is the set
-20 < x < 5.
But due to the meaning of x, the dimension x must be positive.
Therefore, the final solution is the set of real numbers 0 < x < 5 meters.
ANSWER. The width must be shorter than 5 meters; the length is 15 meters greater than the width.
Solved.