Question

a number consists of two digits whose sum is 9 if 27 is subtracted from the number its digits are reversed

Answer 1

the right answer is 63.

Answer 2

let the digit be XY
X+Y=9
X=9-Y
(10X+Y) - 27 = (10Y+X)
10X+Y-10Y-X = 27
9X-9Y=27
9(9-Y) - 9Y = 27
81-9Y -9Y=27
-18Y= 27-81 = -54
Y= 54/18= 3
⇒X= 9-3= 6
Therefor the digit is 63 and the reversed version is 36