From Förberedande kurs i matematik 1

Individually, the terms are difficult to calculate, but the two logarithms can be lumped together using the logarithm law, \displaystyle \log a - \log b = \log\frac{a}{b}\,,

\displaystyle \lg 50 - \lg 5 = \lg\frac{50}{5} = \lg 10 = 1\,\textrm{.}