In a row, Soniya is seventh from the left end and

Solution

As, Soniya is 7th from the left and Bharti is 12th from the right. When they interchange their positions, then Soniya is 12th from the right and Bharti is 7th from the left. It is given in the question that Soniya is 16th from the left end after interchanging the position. So, Soniya sits to the right of Bharti, so the number of persons in the row is (16 + 12 - 1) = 27. So, Bharti's position from the right end is: (27 - 7 + 1} = 21^st.