kill(all)$

van=facebook.com/LearningCalculus$

f(L):=(L[1]+L[2])*100+(L[1]+L[3])*10+(L[2]+L[3]-L[1])*1;

f([5,4,2]);

f([3,2,3]);

f([2,4,0]);

f([1,5,2]);

expand(f([x,y,z]));

solve(f([x,y,z]),z);