Answer:
1) given
2) given
3) definition of vertical angles
4) AAS
Step-by-step explanation:
Each number is added by 3 so it's 17 20 23 26 29 32 35 38 41 and so on.
8 balls = 16
1 ball = 2
32 balls = 64
David will finish first, because if you divide Brad's miles by 2 to his miles in a 1/4 of an hour are 5.95 miles. This means David went 6.2 miles in the same time that Brad went 5.95. Therefore, David will finish first.
It's a factor. This concept is widely used throughout algebra, and you'll probably bump into it through the end of high school and beyond.
A common use is expressing a term in <em>prime factorization</em>, or reducing a number to its most base parts- primes. For example:

Of course, a number like 13 which is already prime is made up of itself and 1. <em>Factors do not have to be primes.</em> 20 is also reducible through combinations of 1, 2, 4, 5, 10, and 20. Prime factorization is just a handy example.
Basically, factors multiply with each other to create other numbers, and numbers can be reduced down to their factors.