In an AP the difference between the 8th term and 4th term is 20 and 8th term is 11/2 times the 4th term. Find the: common difference and the first term of the sequence

a+7d - (a+3d) = 20

4d=20
d = 5
a+7d = (11/2)(a+3d)
a+35 = (11/2)(a+15)
2a + 70 = 11a + 165
-9a = 95
a = - 95/9