Convert the logarithmic equation into exponential form. The statement log_10(x + 8) = 5 means x + 8 = 10^5. Now calculate 10^5 = 100000, so x + 8 = 100000. Subtract 8 from both sides: x = 100000 - 8 = 99992. Finally, check the domain: x + 8 must be positive, and 99992 + 8 = 100000 > 0, so the answer is valid.