Answer:
a=1
Explanation:
If the number is divisible by 9 the sum of its digits is divisible by 9 as well.
The numbers 18 , 27, 36 are divisible by 9 . Check each of them.
a+a+4+4+8=2a+16=18
2a=2
a=1
2a+16=27
2a=11
a=5.5 -it is not the digit . So is not the solution.
2a+16=36
2a=20
a=10 is not a digit, so isn't a solution
any bigger number divisible by 9 (45,54,63...) wil not give the digit.
So there is only 1 solution a=1