Find the first term and the common different of an arithmetic progression if the sixth term is

Question

25 and the sum of the six terms in the progression is 80.

Answer 1

a + 5d = 25 or a = 25-5d

sum(6) = 3(2a + 5d) = 80
6a + 15d = 80
6(25-5d) + 15d = 80
150 - 30d + 15d = 80
-15d = -70
d = 70/15 = 14/3
then a = 25 - 5(14/3) = 5/3

your turn to finish it