By the looks of it the output from
int num = 0, den = 0, num2 = 0, den2 = 0;
cout << "What is" << num<< "/" << den<< "*" << num2<<"/"<<den2<<"?"<<endl;
will be: What is0/0*0/0?
Is that what you expected it to display? If not, what did you expect it to display? Did you expect it to display values contained in num, num2, den and den2 some time AFTER this statement is executed (mathematicians who are new to programming often make that mistake)?