Question 1154119
{{{ 1/4 }}} is Mary's rate: [ 1 job ] / [ 4 days ]
{{{ 1/6 }}} is husband's rate: [ 1 job ] / [ 6 days ]
----------------------------------------------------
 Let {{{ t }}} = time in days for job to get done 
with them working together
Add their rates of working
{{{ 1/4 + 1/6 = 1/t }}}
Multiply both sides by {{{ 12t }}}
{{{ 3t + 2t = 12 }}}
{{{ 5t = 12 }}}
{{{ t = 2.4 }}} days
They get it done in 2.4 days
--------------------------------
check:
{{{ .25 + .1667 = 1/2.4 }}}
{{{ .41667 = .41667 }}}
OK