Answer: The balanced chemical equation is written below.
Step-by-step explanation:
Single displacement reaction is defined as the reaction in which more reactive element displaces a less reactive element from its chemical reaction.
The reactivity of metal is determined by a series known as reactivity series. The metals lying above in the series are more reactive than the metals which lie below in the series.

Metal A is more reactive than metal B.
Tin lies above in the series than hydrogen. So, it displaces hydrogen from its chemical reaction and releases hydrogen gas.
The chemical reaction of tin and hydroiodic acid follows the equation:

Hence, the balanced chemical equation is written above.