$$(31-11)\div2=10.$$ 
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? 
Options:
  $$10$$ 
  $$21$$ 
  $$20$$ 
  $$15$$ 