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
Find the first term and the common different of an arithmetic progression if the sixth term is
25 and the sum of the six terms in the progression is 80.
1 answer