Find the 20th term of the A.P. whose 7th term is 24 less than the 11th term, first term being 12.

Given, a = 12 and a₁₁ - a₇ = 24 (Eq 1)

By using formula a_n = a + (n - 1)d for Eq 1 we get,

⇒ a₁₁ - a₇ = 24
⇒ a + (11 - 1)d - [a + (7 - 1)d] = 24
⇒ a + 10d - a - 6d = 24
⇒ 4d = 24
⇒ d = 6.

20th term of A.P. is,

a₂₀ = 12 + (20 - 1)6 = 12 + 19 × 6 = 12 + 114 = 126.

Hence, the 20th term of the A.P. is 126.