Noah is helping to collect the entry fees at his school's sports game. Student entry costs $2.75 each and adult entry costs $5.25 each. At the end of the game, Diego collected $281.25. Select all equations that could represent the relationship between the number of students, s, the number of adults, a, and the dollar amount received at the game.

281.25 − 5.25 a = 2.75 s
a = 53.57 − 2.75 5.25 s
281.25 − 5.25 s = a
281.25 + 2.75 a = s