heres a quick overview of my problem for a triple integral i have:

(((_v where bracket is integral sign lol.

where V is the region bounded by the planes x+y+z=a, a>0, x=0, z=0.

my notes say the limits are 0<x<a ,a-x<y<a , a-(x-y)<z<0 for dzdydx.

if i rearrange x+y+z=a i can never come up with the limits i have written down or have a clue how to... how do i get the limits! thanks so much.