In a school there are 6 boys and 23 girls. 33 more girls joined the school. How many more girls than boys does the school have?
There are 6 boys and 23 girls in the school. 

33 more girls joined the school. 

That means there are now 56 girls in the school. 

There are still 6 boys in the school. 

That means there are 50 more girls than boys in the school.