Let the hundredth digit of this three-digit number be A, the tenth digit be B and the unit digit be C, then this three-digit number is (100a+ 10b+c).

a+b+c= 12

b-c=2

100 a+ 10 b+c-( 100 c+ 10 b+a)= 99

So, a=4, b=5 and c=3.

This three-digit number is 453.