help find the denominator

Please let me know how to solve this question

I am not sure what the title of this thread has to do with the problem, but...
To solve this you will want to solve for in the first equation, then substitute that into the second equation. Now solve for in the second equation, then substitute that and what you got for into the third equation. At this point the third equation should be in terms of only. Finally, sovle for . This last step will give you a number. Now use this to determine and finally use both to determine .