Hi,

Jack usually mows his lawn in 3 hours. Marilyn can mow the same yard in 7 hours.

Let x represent the time it takes them together

1/3 + 1/7 = 1/x

Mulitply thru with 21x to clear the denominators

7x + 3x = 21

10x = 21

x = 2.1 hrs together 

RELATED QUESTIONS

Jack usually mows his lawn in 7 hours. Marilyn can mow the same yard in 5 hours. How much  (answered by dabanfield,Alan3354)

Please help me to solve : Jack usually mows the lawn in 3 hours. Marilyn can mow the same  (answered by Edwin McCravy)

Jack usually mows his lawn in 5 hours. Marilyn can mow the same yard in 4 hours. How much  (answered by mananth)

Jack usually mows his lawn in 5 hours. Marilyn can mow the same lawn is 3 hours. How much  (answered by solver91311)

jack usually mows his lawn in 3 hours. Marilyn can mow the same yard in 7 hours. How much  (answered by scott8148)

Jack usually mows his lawn in 3 hours. Marilyn can mow the same yard in 7 hours. How much  (answered by ewatrrr)

Jack usually mows his lawn in 3 hours. Marilyn can mow the same yard in 6 hours. How much  (answered by nerdybill)

Hi story problems are not favorite and seem to get confused with them. Can you please... (answered by nerdybill)

Jack usually mows his lawn in 6 hours. Marilyn can mow the same yard in 3 hours. How much  (answered by checkley77)