//I coded this question in python here is how i got the ans 25:
from numpy import integer
count=0
finalcount=0
for i in range (100,999):
if i/18 == int(i/18):
count= count + 1
n=i
if sum([int(d) for d in str(n)])==18:
finalcount= finalcount + 1
print(finalcount)
// answer is 25