Question

0,0064=9*10^9*(0,0008х/3000^2)

Answer 1

$0,0064=9\cdot10^9\cdot(\frac{0,0008x}{3000^2})\\\\9\cdot10^9\cdot\frac{8\cdot10^{-4}x}{(3\cdot10^3)^2}=64\cdot10^{-4}\ /:10^{-4}\\\\9\cdot10^9\cdot\frac{8x}{9\cdot10^6}=64\\\\10^3\cdot8x=64\ /:10^3\cdot8\\\\x=\frac{8}{1000}\\\\x=0,008$