Answer:
a₄₃ = 181
Explanation:
there is a common difference between consecutive terms in the sequence, that is
17 - 13 = 21 - 17 = 4
this indicates the sequence is arithmetic with nth term
= a₁ + (n - 1)d
where a₁ is the first term and d the common difference
here a₁ = 13 and d = 4 , then
a₄₃ = 13 + (42 × 4) = 13 + 168 = 181