In a row of girls facing North, Riyana is 12th to the left of Pari , who is 31st from the right end. If Avinash, who is 16th form the left end, is fourth to the right of Riyana , how many girls are there in the row?

54

Pari is 31st from right and Riyana who is 12th to the left of Pari . So, Riyana is 43rd from right.

Avinash is 4th to the right of Riyana . So, Avinash is 39th from the right. Also, Avinash is 16th from the left.

Therefore, Number of girls in the row = (39 + 16 - 1) = 54