What do you have to do? Solve the system? ...
The first thing I noticed is that you recognize two equal parts in both equations, the part and
So you can 'simplify' the system by saying, let and therefore you get the two simultaneous equations:
Solve this system and afterwards do the back-substitution.
I'll give you a part of the solution,
Solving the system by reforming (1) to and substituting this in (2):
Two solutions: or
But we have to reject because is always >0.
So now you can do the back-substitution and solve it.