What is the surface area of the regular pyramid 

At a sale this week, a desk is being sold for $213. this is a 29% discount from the original price. what is the original price?

If, while training for a marathon, you ran 60 miles in 2/3 months, how many miles did you run each month? (assume you ran the same amount each month) write your answer as a whole number, proper fraction, or mixed number in simplest form. you ran __ miles each month.

Can you me find the missing length. i attached an image.