1) Add 1 & 3 to get 4.
2) Divide 2400 by 4 to get 600.
3) Than times 600 by 1 to get 600.
4) Than times 600 by 3 to get 1800.
5) Finally you will have the answer:
600:1800.
To make sure this is correct, add 1800 & 600 together and you will have 2400.
Answer is then: 600:1800!
Hope this helps!!