Question

the sum of 2 digits in a2 digit no is 7.if we add 9 to it the digits are interchanged.find the no

Answer 1

let the ones digit no. x
then tens place digit is 7-x
then the no. will be 10(7-x)+x
                             70-9x
acoording to the question
70-9x+9=9x+7
         18x=72
            x=4
therefore the no. is 34