(i)

a = 7, d = 3

A_n = 43

a + (n – 1) d = 43

7 + (n – 1) 3 = 43

3n = 39

n = 13

Therefore, there are total 13 terms in the A.P.

(ii)

a = -1, d =

A_n =

a + (n – 1) d =

-1 + (n -1) =

n = 26

(iii)

a = 7, d = 6

A_n = 205

a + (n – 1) d = 205

7 + (n – 1) 6 = 205

6n = 204

n = 34

(iv)

a = 18, d =

A_n = -47

a + (n – 1) d = -47

18 + (n – 1) = -47

18 - + = -47

n = 27