Question 1067976
Add their individual rates of working to 
get their rate working together
Let {{{ t }}} = Krista's time in hrs to do 1 job
----------------------------------------
Melissa's rate of working:
[ 2 jobs ] / [ 3 hrs ] = {{{ 2/3 }}} jobs/hr
Krista's rate of working:
[ 1 job ] / [ t hrs ]
Their rate working together:
[ 8 jobs / 3 hrs ]
---------------------------
Add their rates of working:
{{{ 2/3 + 1/t = 8/3 }}}
Multiply both sides by {{{ 3t }}}
{{{ 2t + 3 = 8t }}}
{{{ 6t = 3 }}}
{{{ t = 1/2 }}}
---------------
Krista takes 1/2 hr to do 1 job
-------------------------------
check answer:
{{{ 2/3 + 1/t = 8/3 }}}
{{{ 2/3 + 1/(1/2) = 8/3 }}}
{{{ 2/3 + 2 = 8/3 }}}
{{{ 2/3 + 6/3 = 8/3 }}}
{{{ 8/3 = 8/3 }}}
OK