Let a be the first term and r be the common difference then t3 = 20 ⇒ a + 2d = 20 ......(i) t7 = 48 ⇒ a + 6d = 48 ......(ii) Subtracting (i) from (ii) we get 4d = 28 d = 7 Putting d = 7 in equation (i) we get a + 2 (7) = 20 a + 14 = 20 ⇒ a = 6 First term = 6 and common difference = 7 then t9 = a + 8d ⇒ 6 + 8 (7) = 62 Hence, 9th term = 62