Question 1
========================================================================
#include<iostream>

using namespace std;

int main(){

    string sentence;
	int j, a=0, e=0, i=0, o=0, u=0;

	cout << "Input: ";
	getline(cin,sentence);

	for(j=0;j<sentence.length();j++){
		if(sentence[j]=='a'||sentence[j]=='A')
			a++;
		else if(sentence[j]=='e'||sentence[j]=='E')
			e++;
		else if(sentence[j]=='i'||sentence[j]=='I')
			i++;
		else if(sentence[j]=='o'||sentence[j]=='O')
			o++;
		else if(sentence[j]=='u'||sentence[j]=='U')
			u++;			
	}

	cout << "a:" << a << endl;
	cout << "e:" << e << endl;
	cout << "i:" << i << endl;
	cout << "o:" << o << endl;
	cout << "u:" << u << endl;
	

	return 0;
}
		
Question 2
=========================================================================
#include<iostream>

using namespace std;

int main(){

    string name1, name2, name3;

    cout << "Name 1:";
    getline(cin,name1);
    
    cout << "Name 2:";
    getline(cin,name2);

    cout << "Name 3:";
    getline(cin,name3);

    if(name1 > name2 && name1 > name2){
        cout << name1 << ",";
        if(name2>name3)
            cout << name2 << "," << name3;
        else
            cout << name3 << "," << name2;  
    }
    else if(name2>name3&&name2>name3){
        cout << name2 << ",";
        if(name1>name3)
            cout << name1 << "," << name3;
        else
            cout << name3 << "," << name1;          
    }
    else{
        cout << name3 << ",";
        if(name1>name2)
            cout << name1 << "," << name2;
        else
            cout << name2 << "," << name1;            
    }

	return 0;
}

----------------------------------------------------------------------

Question 3
#include<iostream>

using namespace std;

int main(){

    string s1, s2;
    cout << "Sentence 1";
    getline(cin,s1);
    
    cout << "Sentence 2:";
    getline(cin,s2);
    
    if(s1.length()>s2.length())
        cout << "longer sentence: " << s1 << endl;
    else
        cout << "longer sentence: " << s2 << endl;

        return 0;
}