=> Program : #include<iostream> #include<math.h> using namespace std; string low2up(string passStr){ string changeStr=passStr; for(int i=0;i<changeStr.size();i++){ if(passStr[i]>=97 && passStr[i]<=122) { changeStr[i]=changeStr[i]-32; } } return changeStr; } bool validHexVal(string checkSr){ bool checkValid; int countNum=0; for(int i=0;i<checkSr.size();i++){ if(checkSr[i]>=65 && checkSr[i]<=70) { countNum++; } if(checkSr[i]>=48 && checkSr[i]<=57){ countNum++; } } if(checkSr.size()==countNum){ return true; }else{ return false; } } int main(){ int decNum=0,val; string hexNum,upperHexNum; cout<<"Enter the hex decimal number "<<endl; cin>>hexNum; upperHexNum=low2up(hexNum); int n=up...