Final answer:
The proper biconditional statement is 'Adding the same expression to both sides preserves equality'
Step-by-step explanation:
The proper biconditional statement formed from the given statement is: If the same expression is added to both sides of an equation, then both sides of the equation remain equal. The correct answer choice is a) Adding the same expression to both sides preserves equality. This statement accurately represents the original statement and the relationship between adding the same expression to both sides and preserving equality in an equation.