Find the transfer function from the system of equations

For example, I have a system of equations, e.g.

$$begin {cases} a_1 x + b_1 y + c_1 z = d_1, \ a_2 x + b_2 y + c_2 z = d_2, \ a_3 x + b_3 y + c_3 z = d_3, end {cases}$$

and for that I have to find $$x / y$$ in the edition. These are just example equations. The real equations may be bigger with more variables, but I need one $$x / y$$ (Transfer function in the output).