1. **State the problem:** Simplify the expression $$\frac{s^{723}}{s^{721}}$$. 2. **Recall the rule for dividing powers with the same base:** When dividing powers with the same base, subtract the exponents: $$\frac{a^m}{a^n} = a^{m-n}$$. 3. **Apply the rule:** $$\frac{s^{723}}{s^{721}} = s^{723-721}$$. 4. **Simplify the exponent:** $$s^{2}$$. 5. **Final answer:** $$s^{2}$$. This means the expression simplifies to $s$ squared.