Solving Simulataneous equations

[smss_engineer]

1. The problem statement, all variables and given/known data

Hi Friends.

Please help me solving two simultaneous equations....
Equations are attached as Jpeg files...

How to solve these two equations(D.17 & D.18) ?? please help me

By SMSS

2. Relevant equations



3. The attempt at a solution

[willem2]

Solve the first one for \eta_g , substitute in the second equation. You get a quadratic equation.