The coefficients are 1 : 2 : 1 : 1
Step-by-step explanation:
To be a balanced equation, the chemical equation should have has equal number of atoms on both reactant and product side.
Given chemical equation:

Now, calculate the number of atoms present in reactant side:
Sn - 1
- 1
K - 1
Br - 1
Then, calculate the number of atoms present in product side:
Sn - 1
- 1
K - 2
Br - 2
Therefore, in order to balance this given chemical equation multiply KBr by 2 on reactant side. So, the balanced chemical equation is as follows.

Hence,
