How do I put a number in the base (a subscript) when trying to find a logarithm answer?

In the calculator on this site you can also specify the base as a second argument to the log function.  For example, enter log(49,7) to get:

$${{log}}_{{\mathtt{7}}}{\left({\mathtt{49}}\right)} = {\mathtt{2}}$$ 

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You can use the change of base rule to calculate this....example........

log₆ 19   =  log 19 / log 6

In general

log_a b =   log b / log a

Thanks, Alan......