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?
Let's denote the number of boys by b, the number of girls by g. 

Then we have the following system of two equations with two unknowns: 

b+g=619

g-b=146

We can solve this system using the substitution method: 

g=619-b

g-b=146

619-b-(619-b)=146

-b=-b

b=b

b=146

Therefore there are 146 more girls than boys in the school. 