Question

How can the indicated logarithm be found? Without a calculator❓

Answer 1

I guess you're supposed to write the expression on the right in terms of
`A,B,C`.

18. Notice that
`729=9^3`, so

`\log_8729=\log_89^3=3\log_89=3B`

20. Notice that
`\frac{14}3=\frac{42}9=\frac{6*7}9`, so

`\log_8\frac{14}3=\log_8\frac{6*7}9=\log_86+\log_87-\log_89=A+C-B`