Bio-control of Parthenium

If 27 @ 22 = 18 and 29 @ 24 = 21, then 12 @ 25 = ?'. What will come in place of question mark?

Select the number combination of letters that when placed sequentially in the blanks of the given series will complete the series.\

By interchanging the given two signs which of the following equation will be not correct?

× and –

Select the option that is related to the third term in the same way as the second term is related to the first term.

ORGANS : SNTZRO : : PARROT : ?

Select the option that is related to the third word in the same way as the second word is related to the first word.

Joy: Delight :: Barrier: ?

Hard : Stone :: Soft : ?

If 24 @ 6 = 28 and 39 @ 24 = 102, then 22 @ 16 = '?'.

Select the set in which the numbers are related in the same way as are the numbers of the following sets:

(7,11, 72)

(5, 8, 39)