Can Any One Please..! Solve This ... Imp..!!! :)

<p>First of all Thank You for your time :)
so,
In 2011 AP Chem FR,there is this equation whose logic in the balancing part I ain't understanding.
Ques)-Solid magnesium hydroxide is added to a solution of hydrobromic acid.</p>

<p>CB answer =Mg(OH)2 + 2H+ --> Mg2+ + 2H2</p>

<p>Why is 2H+ written in the reactant rather than HBr ?
This thing is troubling me in almost all balancing equation questions!!!!!
Help appreciated</p>

<p>If you read the instructions before attempting to solve the problems, you’ll see this:

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