algebra
posted by becky .
Jack usually mows his law in 5 hours. Marilyn can mow the same law in 6 hours. How much time would it take for them to mow the lawn together?

Add the RATES that they mow lawns.
1/6 lawn/h + 1/5 lawn/h = 11/30 lawn/h
The combined rate times the time reT equals one lawn
11/30 * T = 1 lawn
T = 30/11 hours 
Add the RATES that they each mow lawns.
1/6 lawn/h + 1/5 lawn/h = 11/30 lawn/h
The combined rate times the time required, T, equals one lawn
11/30 * T = 1 lawn
T = 30/11 hours