Seemingly there's no overwhelming interest to kick anybody. So, here's a kick.
See the next simple (much simpler than your system) block diagram and the equations which show the same math as the drawn blocks:
The boxes have linear transfer functions A,B, C and D. They contain numbers and some of them may also have the Laplace variable s.
x, v, y and z are the signal variables, actually signal Laplace transforms.
The transfer functions affect by multiplying the variables. The summing junction generates the sum v.
Your job is to reduce the equation set to one by eliminating intermediate variables v and y. The remaining equation contains the transfer functions, the input x and the output z. It will be z=Hx where H is the wanted transfer function between x and z. H can be simple or complex depending on the block transfer functions and the circuit. It can well contain s and its powers as well in the nominator and in the denominator.
In this case A,B,C and D are not defined with finer details, so you'll end to z=Hx where the final transfer function H=AC/(1+ACD+AB)
End.