Some examples:

“I need a lesson of chemistry, as I am clear about acids and redox”

“Need a lesson of Maths, pls explain me limits”

“Need to practice about Mechanics, circular motion, pendulum and springs”

“Pls help me on chemical bonds”

“Need few clarifications on Electromagnetism and Maxwell equations”

“Pls some support on basis of Statistics to prepare a University test”

“can you explain me some principles of Economics ?”

“ for my start-up I need to prepare a business plan next week, can you help me?”