the first term of an ap is -8 the ratio of the 7th to the 9th term is 5:8 calculate the common difference of the progression

Answer 1

(-8+6d)/(-8+8d) = 5/8
now just solve for d

Answer 2

a7=a+6d...(1)a9=a+8d....(2)a7:a9=5:8a+6d/8+8d=5/8(a=8) 64+48d=40-48d 24=-8d d=-3