There are $$600$$ pupils in Pip\textquotesingle s school, with $$30$$ more girls than boys. How many girls are at Pip\textquotesingle s school? 
Overseas Competition->Knowledge Point->Word Problem Modules->Questions Involving Sum, Difference and Multiples->Problems Involving Sum and Difference
Let there be $$g$$ girls in Pip\textquotesingle s school. Then there are $$(g-30)$$ boys at the school. So $$g+g-30=600$$. Therefore $$2g=630$$, that is $$g=315$$. 