#### Answer

227,000,000

#### Work Step by Step

$820,918,446\approx821,000,000\ \longrightarrow$hundred-thousands position is $\geq$5, round up
$593,688,638\approx594,000,000\ \longrightarrow$hundred-thousands position is $\geq$5, round up
$\ \ \ \overset7/\!\!8\overset{11}/\!\!\!2\overset{11}1,000,000$
$\underline{-5\,9\,4,000,000}$
$\ \ \ 2\,2\,7,000,000$