Solution:

 Provided that,

 a₃ = 12 is the 3^rd term

 a₅₀ = 106 is the 50^th term

We all know that,

12 = a+2d ……………………………. (i)

Similarly,

106 = a+49d …………………………. (ii)

  (ii) – (i), we get

94 = 47d

d = 2 = common difference

From the equation (i), we get,

12 = a+2(2)

a = 12−4 = 8

a₂₉ = a+(29−1) d

a₂₉ = 8+(28)2

a₂₉ = 8+56 = 64

As a result, 64 is 29^th term.