The first term is a which is equal to 14.5
The 4th term is a + 3d = 18.4
We know what a is so we can substitute it into the above equation...
14.5 + 3d = 18.4
3d = 3.9
d = 1.3
So the common difference is 1.3... now you just have to add that to the first term so...
14.5 + 1.3 = 15.8 (2nd term)
15.8 + 1.3 = 17.1 (3rd term)
Hope this helps! Any questions let me know:)