Answer
Greatest income--males in sales jobs
Least income--females in service jobs
Work Step by Step
males in service--$x$
males in sales--$y$
females in service--$b$
females in sales--$c$
$x = 120 + b$
$c = y - 289$
$x = 2b - 303$
$y = 2c - 227$
$120 + b = 2b-303$
$120+b-b+303=2b-303-b+303$
$423 = b$
$c =y-289$
$y=2c-227$
$c=y-289$
$c+289=y-289+289$
$c+289 = y$
$2c-227 = c+289$
$2c-227-c+227=c+289-c+227$
$c = 516$
$x=120+b$
$x=120+423$
$x=543$
$y=c+289$
$y = 516+289$
$y=805$
