Let x be the smaller dimension, in meters (the width).


Then the larger dimension (the length) is (x+3) meters, according to the condition.



They want you determine x in a way to satisfy inequality

    x*(x+3) < 18.


It is equivalent to 

    x^2 + 3x - 18 < 0,


or, in factored form

    (x+6)*(x-3) < 0.


The solution to this inequality is the set

    -6 < x < 3.


But due to meaning of x, the dimension x must be positive.


Therefore, the final solution is the set of real numbers  0 < x < 3 meters.


ANSWER.  The width must be shorter than 3 meters;  the length is 3 meters greater than the width.