The correct first step in establishing that \( \log(10^7 \cdot 5) = 7 + \log 5 \) is:
The first step is to rewrite the expression using addition, such that \( \log(10^7 \cdot 5) = \log(10^7) + \log(5) \).
This uses the property of logarithms that states \( \log(a \cdot b) = \log(a) + \log(b) \). From there, you can then move the exponent in front of the logarithm, yielding \( \log(10^7) = 7 \). Therefore, it leads to the final expression.