Let abc be the three digit number.
Given abc = a + b + c +459 .......(i)
Again abc=100a+10b+c...........(ii)
From equation(i) and (ii), we get
100a + 10 b + c = a + b + c + 459
100a - a + 10b - b + c - c =459
99a + 9 b = 459
9(11a + b) = 459
11a + b = 51 .....(iii)
To find: ab+a=10a+b+a
=11a+b
∴ab+b=51 [From equation(iii)]