$$(31-11)\div2=10.$$ 
Grandma made some cheese dumplings and some blueberry dumplings. Altogether, she made $$31$$ dumplings. If she had made $$11$$ more cheese dumplings, then there would be the same number of blueberry dumplings as cheese dumplings. How many cheese dumplings did grandma make?（$$2009$$ Math Kangaroo Problem, Levels $$1-2$$, Question \#$$19$$） 
* $$10$$ 
* $$21$$ 
* $$20$$ 
* $$15$$ 