Answer: Jenny = 6 | Kim = 7 | (Unknown Sister because no name) = 44
Explanation:
Jenny = 6 years (that we already know)
6 x 2 = 12 - 5 = 7 years for Kim
7 + 6 = 13
To find the unknown age of the last sister, we will subtract 57 - 13 = 44
So the last sister is 44.
(I am very sorry if this is wrong, I am only in Middle School).