Transform the circuit of combinational logic into a boolean expression

Question

We have the following:

I want to transform this circuit of combinational logic into a boolean expression.

The circles mean the negation and the symbol that is used is the symbol for AND, or not?

To find that expression do we start from right to left?

Answer 1

You can start from left. If there is single input NAND gate then you should assume the other input is absent that is 0. So the top most gate in left is NOT(0 AND $x$)=1 Similarly for bottom most gate it is also 1.

The final expression should be $f_{x,y,x}=yz$