Hydrogen gas has a density of $0\mathrm{.}090\frac{g}{L},$ and at normal pressure and $-0\mathrm{.}129C$ one mole of it takes up $22\mathrm{.}4L.$ How would you calculate the moles in $870$ g of hydrogen gas?

Set the math up$.$ But don't do any of it$.$ Just leave your answer as a math expression.

Also, be sure your answer includes all the correct unit symbols.

moles $=\frac{870(g)}{0\mathrm{.}090g{L}^{-1}}$