Let's say the user makes a choice to buy a TV, so then they are asked if they would like to add insurance and then those two values are added to the subtotal and then tax is added and finally the total. For example

double subtotal = 0.0
double tax = subtotal * .06
double total = tax + subtotal

else if ( choice == 'B' )
{
subtotal + 300.00
cout << "Add insurance ($32.00)? Y/N: ";
cin >> choice;

if ( choice == 'Y' )
{
subtotal + 32.00 ;
}

else if ( choice == 'N' )
{
subtotal + 0.0
}

else
{
cout << " You did not make a correct choice, quitting program " ;
return 0 ;
}

cout << " Your Subtotal is: " << subtotal << endl;
cout << "Tax: " << tax << endl;
cout << " Total: " << total << endl;
return 0 ;

Choice B means they are choosing to buy the TV.
When I run this I just get 0.0 out for all values, so can anyone help me with this? So that if the user orders the tv and insurance the subtotal should be 332.00 and then the rest should work out.