We are given the definition of the glider ratio: movement forward divided by movememnt down.
We are given the movement forward (840 feet), and the movement down (80 feet).
Applying the definition, we divide the two quantities:
[tex] \text{glider ratio} = \dfrac{\text{movement forward}}{\text{movement down}} = \dfrac{840}{80} = 10.5 [/tex]
