If a common logarithm is written without a base, what base should be used in evaluating it?

10

Step-by-step explanation:

By convention we denote log of any number to base e as ln.

In mathematics and Calculus, whatever we do for log functions mean log to base e only.

But for practical uses, since we are using decimal system for numbers and numbers have place values in powers of 10, common logrithm is used.

Common logs have base 10 and used for calculation especially in Physics and Maths experiments

Hence a common logrithm written as log without any base means it implies that the base is 10