int highest = number1; //just a guess, we will see if it is true
if(number2 > highest)
highest = number2; //it is not true, number2 is higher, readjust our guess
if(number3 > highest)
highest = number3; //it is not true, number3 is higher, readjust our guess
std::cout << "Highest: " << highest;
I think u can figure out the code for smallest by yourself