Math/Riddle to solve: How can i find out the answer?

[✉Nαeniα✉]

Peter can cut the turf in 2 hours.
John can cut the turf in 3 hours.
Susie can cut the turf in 5 hours.
Mayra can cut the turf in 8 hours.

If they all worked together on the hallowed turf, each working at his or her same speed as before, how long would the task take ?
Thanks mwcritt.
Was having trouble finding the format to solve it

 

[R.N.]

It would take 8 hours. It is that Susie, John and Peter would finish before Mayra would.

 

[mwcritt]

1/2 x + 1/3 x + 1/5 x + 1/8 x = 1 (1 means the whole job)
solve for x

 

[ironduke8159]

x/2+x/3+x/5+x/8 = 1
60x + 40x + 24x + 15x = 120
139x = 120
x = 120/139 hours = approximately 51.8 minutes