Correct option is C
Let A be apple and O be oranges.
12A + 15O = 660
15A + 21O = 870
Solving them we get
60A + 75O = 3300
60A + 84O = 3480
So we get, 9O = 180, O = Rs. 20
Put in the first equation
12A + 300 = 660
12A = 660 – 300 = 360
A = Rs. 30