Let the answer be x. That is, it would take them x hours if they worked together.
So their harvesting rate is 1 field per x hours,
or 
.
Danielle can harvest a field in 16 hours.
So Danielle's harvesting rate is 1 field per 16 hours,
or 
.
Kathryn can harvest the same field in 12 hours.
So Kathryn's harvesting rate is 1 field per 12 hours,
or
.
Find how long it would take them if they worked together.
The equation comes from








Multiply that equation through by the LCD = 48x and solve for x and you'll
get
or
hours.
Edwin