The Gemara cites a B’raisa that the pious would spend an hour in meditation before davening, and hour in davening and an hour in meditation following davening.
Question: If they did this for three tefillos per day how many hours did they spend a day doing things other than meditation and davening? (Brochos 32b)
Answer: 3 x 3 = 9
24 – 9 = 15 hours