Answer:
153.8 I guess... this is your answer
(2x - 1) (x + 7) is the answer to your question!

is equation of circle which have radius equal 5 and center in (0,0) point
The proportion of 16 to 4 is 4 is 1/4 of 16( 4/16 = 1/4)
So x would be 1/4 of 12
12/4 = 3
X = 3