Complex sentence: During adolescence, formal operations are developing and become more and more intact and present in thinking processes and according to Piaget allows for "the young person to construct all the possibilities in a system and construct contrary-to-fact propositions".
Split into simpler sentences: During adolescence, formal operations are developing and become more intact and present in thinking processes. According to Piaget, these formal operations allow for "the young person to construct all the possibilities in a system and construct contrary-to-fact propositions".