Find the value of `^(20)C_4 + ^(20)C_5`

Find the value of ^(14)C_5

Find the value of ^(15)C_4

Find the value of ^(20)C_16 - ^(19)C_16 = ((20!)/(4! * 16!)) - ((19!)/(3! * 16!))

Find the value of ^(15)C_4 + ^(15)C_5 =

Find the value of sum_(r=1)^4 ^(21-r)C_4

Find the value of (a) ""^(15)C_(4) , (b) ""^(80)C_(2) ( c) ""^(15)C_(4) + ""^(15)C_(5) , (d) ""^(20)C_(16) - ""^(19)C_(16)

Solve the following subquestion: If a/b = 5/2 , find the value of (20b +7b)/(20b -7a)