Alguien que me ayude :)​

[a] See attached

  - Her chance of making it is 1/3, 1 - 1/3 = 2/3, so her chance of missing is 2/3

[b] 1/2 or one half

First chances (hit and hit): 1/4 * 1/3 = 1/12

Second changes (hit and miss): 1/4 * 2/3 = 2/12

Third chances (miss and hit): 3/4 * 1/3 = 3/12

(when multiplying fractions you multiply across)

Adding all chances together: 1/12 + 2/12 + 3/12 = 6/12 = 1/2

Have a nice day!

  I hope this is what you are looking for, but if not - comment! I will edit and update my answer accordingly. (ノ^∇^)

- Heather