First you would need to find what 1 is in terms of the ratio, and you can do this by adding up 4, 5, and 9 to make 18, and then dividing 180 by 18 which is 10. Now that you know this, you just multiply it by 4, 5, and 9 to get the answer, so:
4 × 10 = 40
5 × 10 = 50
9 × 10 = 90
So your answer would be 40:50:90, I hope this helps!