To find FDH and FDE you first need to solve GDH.
Here’s how to set up GDH.
8x-1=6x+15
Subtract 6x from both sides so that it cancels out.
2x-1=15
Add 1 to both sides so that it cancels out.
2x=16
Divide by 2z
x=8
Plug in.
GDH: 8(8)-1+6(8)+15=78
FDH: 122+78= 200
FDE: 122+15=137