I have the example log 2 8 = 3
but i cant figure out what keys to press on the calculator to work this out myself! help please!
The point of these problems is to help you understand what the $\displaystyle log$ function actually entails. $\displaystyle log_{a}b=x \Rightarrow a^{x}=b$ Applying that to the one you have:
$\displaystyle log_{2}8=x \Rightarrow 2^{x}=8$ The answer should be somewhat obvious.
If you must use a calculator (rather than the simpler definition of logs), then you'll need to use the change-of-base formula to convert the base-two log to either a base-10 or base-e log.
. . . . .$\displaystyle \log_b(x)\, =\, \frac{\log_a(x)}{\log_a(b)}$
...where "b" is the original base and "a" is the base you're changing to.
(The answer will be the same, regardless of the base you choose. But you have to use a base that your calculator can understand.)