1. The problem is to write the four numbers $1.2 \times 10^{-7}$, $2.3 \times 10^{5}$, $5.76 \times 10^{-2}$, and $7.81 \times 10^{3}$ in ascending order. 2. First, convert all numbers to standard decimal notation for easier comparison: - $1.2 \times 10^{-7} = 0.00000012$ - $2.3 \times 10^{5} = 230000$ - $5.76 \times 10^{-2} = 0.0576$ - $7.81 \times 10^{3} = 7810$ 3. Now compare the decimal values: $0.00000012 < 0.0576 < 7810 < 230000$ 4. Therefore, the four numbers in ascending order are: $$1.2 \times 10^{-7}, 5.76 \times 10^{-2}, 7.81 \times 10^{3}, 2.3 \times 10^{5}$$