I have jut this and I don't know how to continue --> log(2x 10)/log100 = log (x 1) -->then 100^2x 10 = x 1 a that is where a ended :/ please help the result should be 3. Thanks everyone ;)

sorry there should be log(2x plus 10)/2 = log(X plus 1)

Just eliminate the log (by applying its inverse function exp):

\log (2x+10)/2=\log(x+1)
\log (2x+10)=2\log(x+1)=\log(x+1)^2
and then
2x+10=(x+1)^2

Obviously you need x>-1 or the first line does not make sense.