D4T:H4P::L5R:________
It can be observed from above
D4T:H4P
D(4)+4=H(8) ( adding 4 to the position of D which is 4)
T20-4=P16 ( Subtracting 4 to the position of T which is 16)
Similarly for L5R
L(12)+5=Q17 ( adding 5 to the position of L which is 12)
R(18)-5=M13 ( subtracting 5 to the position of R which is 18)
Hence, D4T:H4P::L5R:Q5M
Find the coefficient of abcd in the expansion of (a+b+c+d)4