factorial

r=5

6!r! (8-r)! =6!r! (6-r)! (7-r)(8-r) = 1

hence 6!r! (6-r)! = ⁶C_r=(8-r)(7-r)

now put values of r and check

r=3,5 satisfy the relation

r can be 5 or 3 both

6!/r!(8-r)!=1

6 x 5 ! = r! (8 - r)!

3! x 5! = r! (8 - r)!

therefore 3! = r! OR 5! = (8 -r)!

it gives r = 3,

OR

5! x 3! = r! (8 - r)!

it gives r = 5.

You can substitute these values in the question and can verify the answer.[1]