The equation of a circle:

(h, k) - a coordinates of the center
r - a radius
A diameter d = 2r
We have

Answer: d = 2 · 10 = 20
Well 100,000=1•10^5
and 1,000,000=1•10^6
(1•10^6)•(1•10^5)
=1•1 10^6+5
=1•10^11 This is your answer in scientific notation but if it was asking you for the answer in standard notation, the answer would be 100,000,000,000.
Hoped I helped!
N-3n=14-4n
N-3n+4n=14
2n=14
N=14÷2
N = 7 To check substitute 7-3(7)=14-4(7)
7-21=14-28
-14=-14