Answer: 36 centimeters.
Explanation:
Given : Area of a rectangular poster = 504 square centimeters.
The width of the poster is 14 centimeters.
We know that area of rectangle :-

Let l be the length of the poster .
Substitute the above values into this , we get

i.e.

Divide both sides bby 14 , we get

Hence, the length of the poster = 36 centimeters.