average problems

This is the cover sheet or tab

AVERAGE STARTING WEIGHT
AVERAGE WEIGHT LOST
AVERAGE % WEIGHT LOSE

These are the colomns i am trying to pull the data from. each person has ther own row


STARTING WIEGHT TOTAL LOST % LOST



I am trying to get the average for the above but the average formula is only letting me do it for it for one sheet at a time and i have 26 sheets or tabs. any help would be awsome