Question 377466
let y = # hours by Yobbie, and j = #hrs by Janice.
y = 2j, and {{{5(1/j + 1/(2j)) = 1}}}.  Then  {{{1/j  +0.5/j = 0.20}}}.
{{{1.5/j = 0.20}}}, or j = 7.5 hrs, for Janice.  Yobbie can finish in 2*7.5 = 15 hours.