I am greater than 4 tens and less than 5 tens I have 9 ones

4 tens = 40 and 5 tens = 50 ... therefore the number has to be between 40 and 50

So: 40 < x <50 ... this says that x is greater than 40 and less than 50

So the possible numbers would be: 41,42,43,44,45,46,47,48,49

Now the number must have 9 ones ... which mean the only number would be 49