Answer :
Let the whole number be x then after decreasing it by 20 you get x-20 which is equal to 69 times it's reciprocal. Then you have, x-20=69(1/x) ⇒ x²-20x-69=0 ⇒ x=23 or -3.
Answer is 23 as we ignore -3 since it is not an whole number.