5n≥25
and if you divide 5 on both sides, n≥5 (I don't know if you are supposed to solve or simply put it in the equation form).
Product refers to multiplication. so 5 and n are being multiplied in the equation.
However, instead of using an equal sign, the sign for "greater than or equal to" must be used. "At least" is a term equivalent to "greater than or equal to".