The difference between the 8th and 4th terms of an AP is 40. If the 8th term is 2/3 times the 4th term.

Find
The common difference
The first term of the AP

4d=40, so d=10

a+7d = 2/3 (a+3d)
a+70 = 2/3 (a+30)
1/3 a = -50
a = -150