the difference between a two - digit number and the number obtained by interchanging the positions of its digits is 81 . what is the difference between the two digits of that number ?
"sol . let the ten ’ s digit be x and unit ’ s digit be y , then , ( 10 x + y ) - ( 10 y + x ) = 81 ⇔ 9 ( x - y ) = 81 ⇔ x - y = 9 answer e"
divide(81, subtract(const_10, const_1))