How is the Zakah(obligatory charity) on articles of merchandise calculated?

(2.5%) of each article`s value is paid as Zakah after a whole lunar year had lapsed.

Is it permissible to give lessons to mixed students of the seventh grade?

It is impermissible to give private lessons to mixed students since such an act leads to serious consequences for the students in this grade are teenagers.

Who is required to fast?

Any adult, sane, and hardship enduring Muslim person is required to fast unless there were prohibiting conditions such as menstruation and confinement.

What`s the ruling on using the following materials in manufacturing cosmetics: olive oil, Vaseline, talc powder, glycerin, honey, almond oil, pine oil, galingale and marjoram?

All perfect praise be to Allah, The Lord of The Worlds, and may His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.

None of the above materials is forbidden, and it`s lawful to use them in manufacturing products that are beneficial to people. This is because, in principle, all things are lawful so long as there is no evidence in Sharia indicating otherwise. And Allah Knows Best.