Question

A number

consisting of
two digits whose sum is 9.
If three times the number is
equal to eight times the
number formed by interchanging
the digits, find the number.​

Answer 1

let the unit digit be x

and the tens digit be y

so x+y = 9 ---> y = 9-x

the number is 10y+x

the number reversed is 10x + y

3(10y+x) = 8(10x + y)

30y + 3x = 80x + 8y

22y = 77x

2y = 7x

2(9-x) = 7x

18 - 2x = 7x

18=9x

x=2

y=7

the number is 72

check:

number is 72

reverse is 27

is 3(72) = 8(27)