Sample space: H1, H2, H3, H4, T1, T2, T3, T4
All outcomes if the card is three: H3, T3
I was unclear about the last two parts of the question.
Answer:
The element you add is 
Step-by-step explanation:
The element you add is 
Remember that

So, in order to complete the square you add 
But when you multiply times
you get

the height is 11.25 because 7×4=28×11.25=315
Answer: 2 . 5
6 4
Step-by-step explanation:
Answer:
b
Step-by-step explanation: