kill(all)$

van=facebook.com/LearningCalculus$

f(x,y,z):=1/x + 2/y - 3/z;

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

result:[]$ max:12$

for x:1 thru max do
    for y:1 thru max do
        for z:1 thru max do
            if  f(x,y,z) = 1 then result : append(result,[[x,y,z]]);

print ("result ", result)$