Twhen you reverse the digitals in a certain number you increase its value by 27. find the number if the sum fixes digits is 9.

The number=10x+y
we suggest this system of equations:
(10y+x)-(10x+y)=27
x+y=9                                ⇒x=9-y

Can solve this system of equations by susbstitution method.
(10y+(9-y)-(10(9-y)+y)=27
10y+9-y-(90-10y+y)=27
10y-y+10y-y=27-9+90
18y=108
y=108/18
y=6

x=9-y
x=9-6
x=3

The number=10x+y=10(3)+6=36

the number is 36.

to check:
63-36=27
6+3=9