Question 765033
{{{ w = k*( 1/t ) }}}
{{{ 12 = k*( 1/10 ) }}}
{{{ k = 120 }}}
and
{{{ 30 = 120*(1/t) }}}
{{{ 30t = 120 }}}
{{{ t = 4 }}}
It will take 4 days for 30 workers 
to build the bridge