If 6x - 4y = 8 8x = 5y + 13 Then what is the value of 6x - 3y?

6x-4y=8 ........ (1) 8x=5y+13 ==> 8x-5y=13 .... (2) (2)-(1) ===> 2x-y=5..... (3) 3*(3) ==> 6x-3y=15

If

a+b=8, a+c=13, b+d=8, c-d=6

Then

a, b, c, d = ??