Question 536988
In this website, I type "{" 3 times, then "log (b,3)=2" and then "}" 3 times to get {{{log (b,3)=2}}}.
I type "{" 3 times, then "log (3)" and then "}" 3 times to get {{{log (3)}}}, which means logarithm of 3 in base 10 (10 omitted).
I assume that's what you meant. You wanted that b as a subscript, right?
{{{log (b,3)=2}}} means that {{{b^2=3}}} and you know what number you have to square to get 3: {{{b=sqrt(3)}}}
I do not see an elegant solution to the other problem. All I can think to do is this:
{{{2^(-x)=.647}}}-->{{{log((2^(-x)))=log(.647)}}}-->{{{(-x)log(2)=log(.647)}}}-->{{{xlog(2)=-log(.647)}}}-->{{{x=-log(.647)/log(2)}}}
and that would give you an approximate value of 0.628.