0.416 = {[PNO]^2 [PBr2]} / {[PNOBr]^2} would be the expression if PNO = PNOBr, then...
[PNO]^2 =[PNOBr]^2, thus expression turns out to be 0.416 = [PBr2] since the [PNO]^2 / [PNOBr]^2 = 1 as expressed in the explanation as 👍/👍. they just didn't show the coefficients, because it didn't matter in this case