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