You have two coins. You want one to have tails, and one to have heads. This is a 50% (1/2) chance for either heads or tails on ONE coin. However, if you want the order you are asked, you have a 1/2 chance that one lands on head and one lands of tail. The reason is this:
There is only 4 different ways it would be resulted:
T= Tails
H = heads
H H, T H, H T or T T
Only T H and H T out of the 4 is valid, therefore 1/2 chance.
