Most fool-proof way to do this in my opinion is to simply expand everything and write it out, i.e.

Throwing this into a calculator, we get
23.032To the nearest cent, this gives us
$23.03
The total number of ways you can toss a coin 3 times is 8.
H H H
H H T
H T H
H T T
T H H
T H T
T T H
T T T
That should be 8 times.
H H T is the only toss that works
1/8 times
Really hope this helps, if you need more help I may be able to go more in depth