Hopefully these are correct lol, make sure to check it with a classmate. but i tried :)
Answer:
7 girls can go in the first place, 6 in the second, etc.
7! ways is the number of ways to arrange the girls.
likewise the boys can be arranged in 7! ways
The total number of ways becomes 7! * 7!
7! * 7! = 25,401 600 ways
(x^3 - y^3)(x^3 + y^3)
You can get this by factoring based on the a^2 - b^2 model