Shall I put "will" in these following subordinate clauses?
He will cook as his mother will show him tomorrow.
I will go where she will stay.
Even though she will study in London, her girlfriend will still stay here.
Thanks a lot!
In the first two, you can use "will", but I don't think native English speakers would do so: I would say "the way his mother shows him tomorrow" (it's unnatural with "as") and "where she stays". This is because there is no true future tense in English, and where future meaning is derivable in other ways, the present can often be used for it.
In the third case, there is nothing that fixes the subordinate clause in the future, so "will" is more likely. But "her girlfriend is staying here" is also possible.