Question 426464
{{{1/8 + 3(1/8 + 1/a) = 1}}}
<==> {{{1/8 + 3/8 + 3/a = 1}}}
<==> {{{1/2 + 3/a = 1}}}
<==> {{{3/a = 1/2}}}
<==> a = 6.  Hence the apprentice can do the whole job alone in 6 hours.