1. The problem is to understand how Step 3 can be applied to all similar equations. 2. Step 3 usually involves simplifying or manipulating the equation using algebraic rules such as factoring, expanding, or canceling common terms. 3. The key formula or rule used in Step 3 is the property of equality: whatever operation you do to one side of the equation, you must do to the other side. 4. For example, if Step 3 involves dividing both sides by a common factor, you write: $$\frac{a}{\cancel{c}} = \frac{b}{\cancel{c}}$$ showing the cancellation of the common factor $c$. 5. This step is universal because it relies on fundamental algebraic principles that apply to all equations of similar form. 6. Therefore, Step 3 can be used in all similar equations because it is based on the invariant properties of equality and algebraic manipulation rules.