just like the previous one, we sum the sides to get the perimeter.

The answer is -8 (-8=2*-4)
The property displayed here is the distributive property.
If you have a variable or unknown number inside or outside of parentheses, you can distribute it to each term and add the terms together, and it will remain true.
Example:
4(x + 5)
After distributing, it'll look like this:
4x + 20
Since we need to find the number of ways they could enter first, second and third place, (I can't demonstrate, but you should get the idea) take 8, 7 and 6 and multiply them, 5-1 we don't need, we just need 8, 7, and 6, multiply those three numbers and you get 336, there you go, 336 ways to organize all 8 girls in first, second and third place, hope this helps