– 12, – 5, 2, 9, 16, 23, 30, . . .

Given A.P. is – 12, – 5, 2, 9, 16, 23, 30, . . .
Here first term a = – 12
Second term t₁ = – 5
Third term t₂ = 2
Common Difference d = t₂ – t₁ = 2 – (– 5) = 2 + 5 = 7
We know that, n^th term of an A.P. is
t_n = a + (n – 1) d
We need to find the 20^th term,
Here n = 20
Thus, t₂₀ = – 12 + (20 – 1) × 7
t₂₀ = – 12 + (19) × 7 = – 12 + 133 = 121
Thus, t₂₀ = 121