The sum of the digits of a two -digit number is 7. If 27 is subtracted from the number the digit interchange their places. Find the number.

Answer 1

10 a + b

a + b = 7
so a = (7-b)

10 a + b - 10*2 - 7 = 10 b + a

10(7-b)+b-20-7=10b+(7-b)

70 -10b+b-27=9 b+7
36 = 18b

b = 2
then a = 5
so
52