Can't figure out how to get the value for "n".

n / 0.005 - n = 1.78     factor out " n '  on the left

n ( 1/0.005 - 1 )  = 1.78     divide both sides by (1/0.005 - 1)

n =   1.78 / (1/0.005 - 1)  ≈  .00894