have derek be x, and jason be y.
this means you can set up a system of equations with:
x+4=y and y-4= 2x-8, or y= 2x-4
since they both equal y, you can set them equal to each other and solve for x
2x-4=x+4
x=8, meaning derek is 8 and if you add 4, that means Jason is 12
JASON IS 12