The correct response is:
The expressions are equivalent because Ella got the same result when she substituted zero for f.
Ella evaluated both expressions \(2f + 3.6\) and \(3f + 3.6\) by substituting \(f = 0\), and both resulted in \(3.6\). This indicates that the two expressions are equivalent for the value substituted. However, it is important to note that just checking one value does not prove the expressions are equivalent for all values of \(f\). They are equivalent if they simplify to the same expression across all values. Since both evaluate to the same result with the same substitution for \(f\), the more accurate conclusion based on her specific work is that they are equivalent for that substitution.