1) 7 * (3^2 - 5) - 7 + 3 = 7 * 4 - 7 + 3 = 24.

2) 4! = 4 * 3 * 2 * 1 = 24.

=>

7 * (3^2 - 5) - 7 + 3 = 4!

It's international-style math notation for factorial)