In the given AP,

First term, a = 7

Common difference, a₂ – a₁ = (11 – 7) = 4

Let the no of terms be n

Nth term, a_n = 139

We know that, For any AP

a_n = a + (n – 1)d

where,

a_n = nth term

d = common difference

n = no of terms

using the above formula for given AP, we have

139 = 7 + (n – 1)(4)

⇒ 4(n – 1) = 132

⇒ n – 1 = 33

⇒ n = 34

Hence, there are 34 terms in given AP.