the K and Cl are 1:1 .. the problem is in the O .. you have 3
(left side) and 2 (right side) .. you multiply the O2 on the right by 3 ..
KClO3 ---> KCl + 3 O2
and now you have 6 O on the right and 3 on the left .. so you multiply the KClO3 by 2 ..
2 KClO3 ---> KCl + 3 O2
now you have 6 O on both sides .. now balance the K and Cl by multiplying KCl on the right by 2 ..
2 KClO3 ---> 2 KCl + 3 O2
