Answer: It is 18.
Explanation:
Those 3 numbers are in proportion with another number that is uknown.
21, 27, 14, and x.
a:b::c:d = a/b::c/d
21/27=14/x
x=14*27 /21
x=18
Because of this, the fourth proportion in 21, 27 and number 14 is 18.
