I need help on this pls

Math it's appreciated. (picture provided)

Using only the digits 5, 6, 7, 8, how many different three digit numbers can be formed if no digit is repeated in a number?

2. there are 250 students in a school auditorium. use numbers from the box to complete the table. 16, 38, 18, 45, 25, 50, 32, 60 grade number percent of all students of students fifth 24 sixth 95 seventh 20 eight 45