Question

124, 213, 338, ..., 720, 989​

Answer 1

Step-by-step explanation:

let n be the number of terms

a = first term, d = common difference , l = last term

$a_{n} = l = a + (n - 1)d \\ \\ 989 = 124 + (n - 1) \times 109 \\ \\ 865 = (n - 1) \times 109 \\ \\ \frac{865}{109} = (n - 1)$