Hey!
She can grade 1/3 of a stack in 1/8 hours. Divide the total amount of stacks by how much she can do.
[tex] 2 \div \frac{1}{3} = \frac{2}{1} \times \frac{3}{1} = 6 [/tex]
Now multiply that by how long it takes her.
[tex] \frac{1}{8} \times 6 = \frac{6}{8} \rightarrow \frac{3}{4} [/tex]
That means it takes her [tex] \frac{3}{4} [/tex] of an hour to grade 2 stacks.
Good luck and hope this helps! :)
