If the digits are a, b and c, the number n is 100a+10b+c
Here are the equations:
a number equals fifteen times the sum of its digits:
100a+10b+c = 15(a+b+c)
if its digits are reversed, the resulting number exceeds n by 396:
100a+10b+c+396 = 100c+10b+a
the one’s digit is one larger than the sum of the other two:
a+b+1 = c
Solving it gives you a=1, b=3, c=5, the number is 135.
