Which of the following letter-clusters will replace the question mark (?) in the given series?

WTDH, URGK, SPJN, ?, OLPT

Select the set in which the numbers are NOT related in the same way as are the numbers of the following set.

(NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into their constituent digits. E.g. 13 - Operations on 13 such as adding/substracting/multiplying etc. to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.)

(5, 13, 16) 

(4, 11, 14)

If '+' means 'subtraction', '-' means 'multiplication', '÷' means 'addition' and '×' means 'division', then what is the value of the following expression?

26 - 13 + 144 × 18 ÷ 81

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

(NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into its constituent digits. E.g. 13 - Operations on 13 such as adding/Subtracting/multiplying etc. to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed)

(60, 15, 40)

(100, 50, 20)