Hi
Not at all easy with such popular names, though Mary Ann's death may be one of the following because she appeared to be in the Leeds area in the censuses, didn't appear after 1871 (I hope) and used her birth date as a guide.
Source, FreeBMD death reg's:
Q4 1877 Mary Ann Walker age 65y, Holbeck, 9b, 223.
Q2 1879 Mary Ann Walker age 67y, Bramley, 9b, 247.
Q3 1880 Mary Ann Walker age 67y, Wortley, 9c, 184.
A popular BI has this, which may be the same Mary as the FreeBMD 1879 death:
27 Jun 1879 Mary Ann Walker age 67y, Leeds, Holbeck Cemetery, bur.
Unfortunately James is not so clear cut as you have probably found out, there are no ages on the FreeBMD and the popular BI is not much help either.
Geoff