how can 2.4+3.6=6?

You first have to add the parts: .4 + .6=1

And you add that to the 2+3=5

5+1=6

$${\mathtt{6}}{\mathtt{\,-\,}}{\mathtt{2.4}} = {\frac{{\mathtt{18}}}{{\mathtt{5}}}} = {\mathtt{3.6}}$$

THAT IS WHAT I GOT WHEN I DID IT BUT HOW DID YOU GET THAT

Thank you now I understand it better but still why is it give me 6