I think you made a typo in your question because I'm pretty sure it would be (y + 4)(5y - 3). If this is the case remember how to do FOIL. First multiply y to 5y and -3 to get 5y^2 -3y, then multiply 4 to 5y and -3 to get 20y -12. Add both of these quantities together to get 5y^2 + 17y - 12. Let me know if you have any questions.