You could factor a 7 out of 7 + 14 to get 7(1 + 2).
This would equal the same thing as 7 + 14, which is 21.
7 * 3 = 21.
21 can be factored like so:
1 * 21 = 21
3 * 7 = 21
The formula for the number of degrees of an external polygon is
360/n where n is the number of sides
octogon has 8 sides
360/8=45
answer is 45 degrees