https://www.gregmat.com/problems/quant?problem=working-at-constant-rates-smith-and-jone
8 hour shift so nancy had just 4 hours remaining, there is no mention she worked extra 4 hours.. i mean normal shift 8 hours + extra 4 hours started earlier to bob
Not quite.
The 8-hr shift is for Bob who started after Nancy had done 4hrs already.
Nancy therefore works for 12hrs.