Math Formula Explained (Thanks Yo)

Think of nine numbers: a, b, c, d, e, and w, x, y, z

Now make five cards:
card1: (a b c d e)
card2: (a+w b+w c+w d+w e+w)
card3: (a+x b+x c+x d+x e+x)
card4: (a+y b+y c+y d+y e+y)
card5: (a+z b+z c+z d+z e+z)

Now, as long as he has to pick from a different row from every card, his sum will always be a+b+c+d+w+x+y+z.

In the video, a=5, b=18, c=31, d=44, e=57, w=12, x=30, y=23,
and z=7.