In a queue of children, Kashish is third from the left end and Mona is eight end from right. If they interchange their places among themselves, Kashish becomes sixteenth from the left end. Then, what will be Mona's position from the right end?

21st

According to the question:

Kashish is 3rd from the left and Mona is 8th from the right. After they interchange the position Kashish is 16th from left. So, according to the statement we can conclude that total number of students are 8 + 16 - 1 = 23 (as 1 position is being counted twice). Thus, Mona's new position from right is 24 - 3 = 21st.