An Arithmetic Pro

First term, a = 5

Common difference, d = 12 - 5 = 7

Using the nth term formula, i.e. a_n = a + (n - 1)d

a₅₀ = a + 49d = 5 + 49(7) = 5 + 343 = 348

Sum of last 10 terms = Sum of 50 terms - sum of 35 terms

Let sum of the last term be S

Using sum of first n terms of an AP formula i.e.

S = 25(353) - 35(124) = 4485