the correct question is
Adrien has 4 liters of milk. He drinks y liters each day. If Adrien has x liters of milk left after one week, express x in terms of y
we know that
y------------> liters of milk that Adrien drinks each day
x-----------> liters of milk left after one week
in one week
Adrien drinks 7y
and
x=4-7y
the answer is
x=4-7y
