To determine whether the expression \(6a−14b+3a−6+21b−18a\) is equivalent to \(-9a+7b−6\), the first property of algebra that should be applied is the Commutative Property.
The Commutative Property allows us to rearrange the terms in the expression, which is helpful when trying to simplify or combine like terms. After applying this property to group like terms together (the \(a\) terms and the \(b\) terms), you can proceed with further operations to see if the two expressions are equivalent.