Answer:
If she works alone, it will take Mary 9 hours to make the costume.
Step-by-step explanation:
The together rate is the sum of each separate rate.
In this problem:
Together rate: 1/6
Sam's rate: 1/x
Mary is twice as fast as Sam, so her rate is 2/x.
Then
[tex]\frac{1}{x} + \frac{2}{x} = \frac{1}{6}[/tex]
[tex]\frac{3}{x} = \frac{1}{6}[/tex]
[tex]x = 3*6[/tex]
[tex]x = 18[/tex]
Mary's rate
2/x = 2/18 = 1/9
If she works alone, it will take Mary 9 hours to make the costume.
