10 separated into 5 groups is 10/5
5 goes into 10 2 times.
10/5=2
The circumference is about 3.14 (

) times bigger than twice the radius. Mathematically, this can be writted as

, where C equals the circumference and r equals the radius, or

where C equals the circumference and d equals the radius.
Remove the parentheses and combine the like terms:
7 - -9 = 7+ 9 = 16
6i - -8i = 6i +8i = 14i
The answer is 16 + 14i