Thanks for your answers,guys! In fact, I was cunning while posting the problem :) I knew the exact solution, it could  be easly found by Mathematica (thanks to toandhsp ) or WolframAlpha or it could be also represented as piecewise function( thanks to Axel Vogt ) or it could be plotted (thanks to Preben Alsholm ). All those approaches could give the answer immediately,but the main idea of the question was to find the way of solving those type of equations without any preliminary preparations like substitutions or plotting or so on. Just using solve,isolve or something (internal to Maple) else (look at Mma Reduce as example).Kitonum, am I right and you are the member of russian forum.exponenta.ru?