The problem is not in the solutions manual and the one it do

The problem is not in the solutions manual and the one it does have (21.10 b) chegg solution is wrong due to a typo.

Solution

Are you sure the concentration of A falls to 0.020 mole dm^-3 as A and B react 1:1 and there is not enought concentration of B to react with 0.055 mol dm^-3 concentration of A.