Chapter 7 - Exponential and Logarithmic Functions - 7-4 Properties of Logarithms - Practice and Problem-Solving Exercises - Page 467: 70

$\dfrac{\log_{10}{140}}{\log_{10}{5}}$ or $\dfrac{\log{140}}{\log5}$

Recall the change of base formula (pg. 464): $\log_{b}{m}=\frac{\log_{c}{m}}{\log_{c}{b}}$ Applying this formula to our equation ($b=5, m=140, c=10$), we get: $\log_5{140}=\dfrac{\log_{10}{140}}{\log_{10}{5}}$