80% of what = 400,000 plz explain i dont know how to do this

Of the 304 people who attended a school play, 5/8 were students. how many of the people who attended were students.

Determine the area of a triangle with (see picture below)

Jessica is organizing a guided tour of the rain forest. the average profit per person that the touring company makes is given by the rational expression 18x+35/x, where x is the number of people going on the tour. what does the numerator of this rational expression represents?