Question 278554
If the problem is:
{{{1 - log(5, (21))}}}
then, since no calculator I know "knows" base 5 logrithms, we need to convert this logarithm to a base our calculator does "know", like base 10 or base e (ln). There is a base conversion formula for this:
{{{log(a, (p)) = log(b, (p))/log(b, (a))}}}
Using this to convert the base 5 logarithm into a base 10 logarithm we get:
{{{1 - log((21))/log((5))}}}
Now you can use your calculators to find the two logarithms, divide them and then subtract that from 1. (Be sure to use this order. Do not divide 21 by 5 first and then find the logarithm. That will not give you the correct answer.)