1. **State the problem:** Calculate the difference between $9.96 \times 10^9$ and $7.44 \times 10^9$. 2. **Formula and rules:** When subtracting numbers in scientific notation with the same power of 10, subtract the coefficients and keep the power of 10 the same. 3. **Intermediate work:** $$9.96 \times 10^9 - 7.44 \times 10^9 = (9.96 - 7.44) \times 10^9$$ 4. **Simplify the subtraction:** $$9.96 - 7.44 = 2.52$$ 5. **Final answer:** $$2.52 \times 10^9$$ This means the difference is $2.52$ billion.