I can help you with the first correct answer first.
The dots represent how many people are at a certain height. Basically 3 people are 78 in.
The choice says that more than half of the players are 79 in or taller. So start at 79 (between 78 and 80).
We see that two players are at 79 in. Now check 80 all the way to 84 (what on earth am I saying-)
Add the dots, starting from 79 all the way to 84. 8 players are 79 in or taller.
Now what about the ones lower than 79? Count those too, starting from 78 to 69. Once you do that, you will see that 7 people are less that 79 in. Which means that more than half of the players are 79 in or taller. That’s how you do it.
For the third one, the tallest player is 84 in. The shortest is 69 in. 84 - 69 = 15. So that’s how the last option is right :)