The answer is 7/20. First, you subtract 2 1/4 and 1 2/5. You have to make a common denominator. The common denominator is 20. Now you have 2 5/20 - 1 8/20. You can't subtract 5 from 8 so you have to regroup. Now you have 1 25/20 - 1 8/20. You get 7/20
What you need to do is subtract 1 2/5 kg from 2 1/4 so first you have to find a common denominator which would be 20 so now it is 2 5/20 - 1 8/20 so now take the 2 5/20 and make it 1 25/20 - 1 8/20 which equals 17/20 kg (I hope you can understand that if you cant sorry that's what I learn how to do that) answer = 17/20
