∵(x-10)² ≥0,|2x-y|≥0,|x-3z|≥0
且(x-10)²+|2x-y|+|x-3z|=0,
∴(x-10)² =0,|2x-y|=0,|x-3z|=0
即x=10,y=20,z=10/3
∴x+y+z=100/3