Create your own : research 10 different shoes or articles of clothing . List specific shoes/articles of clothing and their current value . Find the median and mode of the costs.

Which one ? is the answer and how to find this answer

Ineed to know the answer to this algebra question.

The fence around a quadrilateral-shaped pasture is 3a^2+15a+9 long. three sides of the fence have the following lengths: 5a, 10a-2, a^2-7. what is the length of the fourth side of the fence?