It is (-15 + 20)/2 = 5/2 = 2.5
15
the answer is 15
The number 20 is.
17... and 19 !
16
35
They are 16, 18 and 20.
(10+20)/2 = 30/2 = 15
The number half-way between is 15. 11, 12, 13, 14, 15, 16, 17, 18, 19 are all between 10 and 20.
10, 12, 14, 15, 16, 18, 20
5, 10, 15 and 20 have five as a factor. The number 16 has five factors.