Question

The fifth term of an arithmetic progression is 11 and its eight term is 19
(a) find its common difference
(b) first term

Answer 1

a+4d=11....1
a+7d=19.....2
sub eq 1 from 2,
3d=8
d=8/3
a=11-4*8/3=11-(32)/3=(33-32)/3=1/3
hence a=1/3. d=8/3

Answer 2

here is your answer, in the picture
hope it helps