1.
4th term = a1 + 3d = 12 (where a1 = first term and d = common difference.)
7th term = a1 + 6d = 20.4
subtract 4th from 7th term, we get:-
3d = 8.4
d = 2.8
So 10th term = 7th term + 3(common difference)
= 20.4 + 3(2.8)
= 20.4 + 8.4
= 28.8 (answer)
All the rest can be answered in the same way.
