Every time you have to compute a certain fraction of some total, you simply need to multiply that total by the required fraction.
So, we start of 2/3 of Rapunzel hair (which you can think of as 1 * 2/3, since all of her hair is the initial total, i.e. 1).
These two-thirds are are new total, and we want to consider the 7/8 of this quantity.
As before, we only need to multiply the values:
[tex] \cfrac{2}{3} \cdot \cfrac{7}{8} = \cfrac{2\cdot 7}{3\cdot 8} = \cfrac{7}{3\cdot 4} = \cfrac{7}{12} [/tex]
