1. **State the problem:** Multiply 8,070 by 99. 2. **Formula used:** Multiplication of two numbers can be done by expanding one number as a sum and multiplying each part. 3. **Rewrite 99 as 100 - 1:** $$ 8,070 \times 99 = 8,070 \times (100 - 1) $$ 4. **Distribute multiplication:** $$ = 8,070 \times 100 - 8,070 \times 1 $$ 5. **Calculate each term:** $$ 8,070 \times 100 = 807,000 $$ $$ 8,070 \times 1 = 8,070 $$ 6. **Subtract:** $$ 807,000 - 8,070 = 798,930 $$ 7. **Final answer:** $$ \boxed{798,930} $$ This method is easier than multiplying directly digit by digit and helps avoid errors.