Question

Sum of a digit of a two digit number...... Answer please

Answer 1

let the ones place digit be x
so tens place digit is 9-x
original number =x+10(9-x)
=x+90-10x
= 9x-90
resulting new number =10x+9-x
=9x+9
a/c to question-
9x-90+9x+9=45
18x-81=45
18x=45+81
18x=126
x=126 ➗ 18
x=7
ones place digit =7
tens place digit =9-x=9-7=2
therefore the resulting new number is 72