In a school there are 362 boys and 257 girls. 403 more girls joined the school. How many more girls than boys does the school have?
There are $b$ boys and $g$ girls in the school. 
$b + g = 619$
$b = 619 - g$
$403$ more girls joined the school. 
$g = 257 + 403 = 660$
$b = 619 - 660 = -41$
There are $41$ more girls than boys in the school.