Were amazed (existanto). Imperfect indicative middle, descriptive of their continued and repeated astonishment. Common verb existhmi meaning that they stood out of themselves as if their eyes were bulging out. The boy had a holy thirst for knowledge (Plummer), and he used a boy's way of learning. At his understanding (epi th sunesei). Based on (epi), the grasp and comprehension from sunihmi, comparing and combining things. Cf. Mark 12:33 . His answers (tai apokrisesin autou). It is not difficult to ask hard questions, but this boy had astounding answers to their questions, revealing his amazing intellectual and spiritual growth.