A and B working together could complete a work in 14 (2/7) days. A takes 7 (2/3) days less than B to finish the work. If A and B start working together and B left the job 5 days before the completion of the job; then find in how many days the work could be completed?

Convert mixed fractions: A and B together take 100/7 days, so their combined rate = 7/100 per day. Let B take x days alone. A takes (x - 23/3) days. Equation: 1/x + 3/(3x-23) = 7/100. Solving gives x = 35 days for B, so A takes 12 days. If B leaves 5 days early, let total time = t days. They work together for (t-5) days, then A works alone for 5 days. Solving: (t-5)(7/100) + 5(1/12) = 1, giving t = 11.42 days.