Marry and Alexis had some stickers in the ratio 7 : 5. Marry and Alexis each gave 20\% of their stickers to Charlotte. As a result, Charlotte\textquotesingle s stickers increased by 80\%. If Mary had 20 stickers more than Charlotte in the end, how many stickers did Alexis have at first? 
Overseas Competition->Knowledge Point->Word Problem Modules->Solving Problems Involving Fractions and Percentages->Percentages Word Problems