Final answer:
The length of DB is 10 meters.
Step-by-step explanation:
To find the length of DB, we can use similar triangles. We have EC = 10 meters and Joe's eye level is 1.2 meters. Since the triangles are similar, we can set up the proportion: EC/DB = Joe's eye level/length of DB. Cross multiplying, we get EC * length of DB = Joe's eye level * DB. Solving for DB, we get length of DB = EC * Joe's eye level / Joe's eye level. Plugging in the given values, we have length of DB = 10 meters * 1.2 meters / 1.2 meters = 10 meters. Therefore, the length of DB is 10 meters.