A number of two digits, written "ab" has value 10a + b
4(a+b) = 10a + b (eq 1)
Reversing the digits means writing it as "ba" which has value 10b + a:
10b + a = (10a + b) + 27 (eq 2)
Simplify both equations:
(eq 1) simplifies to 2a - b = 0 ---> b = 2a
(eq 2) simplifies to b - a = 3
Using substitution (b = 2a) into the simplified (eq 2) gives
2a - a = 3 or a = 3 ---> b = 6
The number is
Check:
4(3+6) = 4*9 = 36 (ok on first condition)
63 = 27 + 36 (ok on 2nd condition)