You cannot solve this without additional information. From what information is provided in the question you may not assume that the relationship is linear.
12 and 5 respectively
-20
(20 + 30)/2 = 25
It is: 1.5*20 = 30 or 10+20 = 30
30
It is: (20+30)/2 = 25
25 is exactly between 20 and 30.
30
11576 * * * * * Actually, GCF(20, 25, 30) = 5
The least common multiple of 20 , 25 , 30 = 300
25 is a perfect square occurring between 20 and 30.
The Least Common Multiple (LCM) of 20, 25, and 30 is 300.