Plz explain this line

Question

X = (z= = - -a)? B:z

Answer 1

i'm not sure because of the space but if its X=(z==--a)?B:z;
its same as
if(z == --a)
X=B;
else
X=z;

Answer 2

that is what is known as the teritary operator. it means "if (first term){
second term
}else{
third term
}

z== --a means "does z equal a - 1?"