You should really state what language you're using. Here it is easily produced in C#, and shouldn't be too much of a hassle to translate to other languages. Note that I did not need to use the iterative variable ( j ), and could instead just use ( i ) in one for loop.
Console.Write("Enter size of triangle: ");
int n = Convert.ToInt32(Console.ReadLine());
for (int i = n - 1; i >= 0; i--)
Console.WriteLine(new String('*', n - i));