View Compilation Error

0_0_33449340_439.cpp: In function 'int main()':
0_0_33449340_439.cpp:21:20: error: 'mon' was not declared in this scope
         if(ifvalid(mon,day,year))
                    ^
0_0_33449340_439.cpp:24:41: error: 'yaer' was not declared in this scope
             cout<<month<<'/'<<day<<'/'<<yaer<<" is an invalid date."<<endl;
                                         ^