I like to give answers along with helpful tips so here ya go. Noun clauses usually always start with a 'w' and relate to who, what, when, why, whom, whichever, whoever whenever.etc So just look for those words.
(don't forget "how" as well)
Answer: Whatever, what
Noun clauses are dependent clauses acting as nouns. They begin with words such as how, that, what, who, whoever, whom, where, when, whether, which, whichever and why. What is more, they can act as subjects, direct objects, indirect objects, predicative nominatives or as objects of prepositions.
Taking all this into account, the noun clauses found in the sentences presented are the following ones: "whatever you do" and "what she should major in at college". In both cases, the noun clauses in question are actings as the subjects of the sentences.
