Question 1023919
Call the number x in the tens place and y in the ones place.  We can then write
xy = 12
and
10y + x = 10x + y + 9  or
9y - 9x = 9  or
y - x = 1
y = x + 1
Now substitute that into the first equation and get
x(x+1) = 12
x^2 + x - 12 = 0
(x + 4)(x - 3) = 0
x = 3
The number must be 34.