Question 356169
Let x = #number of seats in the airplane.  Only {{{2x/3}}} seats are occupied.
Of these, {{{(1/5)*(2x/3)=2x/15}}} are boys, {{{(1/4)*(2x/3)=x/6}}}are women, {{{(1/8)*(2x/3)= x/12}}}are girls, and 68 are men.  Hence,
{{{2x/15+x/6+x/12+68 = 2x/3}}}, or
{{{68 = 2x/3-2x/15-x/6-x/12}}}, or
{{{68 = 17x/60}}},
{{{x = 4080/17 = 240}}}.
Therefore there are 240 seats in the airplane all-in-all.