Respuesta :

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.