foo.cc: In function 'int main()':
foo.cc:8:10: warning: unused variable 'x' [-Wunused-variable]
   double x;
          ^
foo.cc:12:23: warning: 'c' is used uninitialized in this function [-Wuninitialized]
   cout <<a*0.2+b*0.2+c*0.6;
                      ~^~~~

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