Questions

A piano is a musical instrument which has keys, pedals and strings in which the strings are struck by hammers.

India play its 1st One Day International match in cricket against England in the year 1974 in Headingley in Leeds.

Every year 5th September is celebrated as Teacher's Day in India, in the memory of Dr. Sarvepalli Radhakrishnan's birthday. He was the first vice-president and second president of India.

After he become the president of India, his students want to celebrate his birthday in grand but he refused and he adviced them to celebrate that day as teachers day. From then, 5th September is celebrated as Teacher's Day.

The logic in the given puzzle is 

Addition of numeric values of corresponding letters in the first three figures gives respective corresponding letter in fourth figure. 

i.e, A = 1 , W = 23 , B = 2 => 2 + 1 + 23 =26 = 'Z'

Similarly, L = 12, K = 11 , A = 1 => 1 + 11 + 12 = 24 = 'X'

Here the missing letter is 'X'.