How many solutions are there to the equation u+v+w+x+y+z=10 where u, v, w, x, y, and z are nonnegative integers, and x is even?
x = 2,4,6,8,10
If x = 10,
u,v,w,y,z = 0
1 CHOICE
If x = 8,
If there is one 2:
5 CHOICE
If there is two 1:
10 CHOICE
15 CHOICE
You keep doing this for all possible combinations, for example x=6, you can do 1111,112,22,13,4
+1439 
