Answer:
It will take Naomi 22 hours
Step-by-step explanation:
If they work together Mark, Naomi, and Yvonne take 11 hours, which means
three people represent 3* 11 = 33 man* hours
If they work alone Yvonne will take 5 man hours, and Mark will take 6* man hours.
Now we know that together they take 33 man hours therefore we have
5+ 6+ N = 33
Where N is Naomi's man* hours. We solve for N and get:
N = 33 - 11 = 22
N = 22
Naomi will take 22 hours to finish the job if she worked alone.
