$$(31-11)\div2=10.$$ 
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, Question \#19） 
Options:
a: $$10$$ 
b: $$21$$ 
c: $$20$$ 
d: $$15$$ 