If you have named tuples you can do this:
results = [t.age for t in mylist if t.person_id == 10]
Otherwise use indexes:
results = [t[1] for t in mylist if t[0] == 10]
Or use tuple unpacking as per Nate’s answer. Note that you don’t have to give a meaningful name to every item you unpack. You can do (person_id, age, _, _, _, _) to unpack a six item tuple.