What is 4.3 as simplest form

If you want to convert 4.3 into a fraction, you can do it like this:
4 equals to 4/1 and 0.3 equals to 3/10.
The result is 4 3/10.

If you want to make it a pure fraction, you have to make one additional step:
because you want to add 4/1 and 3/10, you have to get the same denominators, so 4/1 changes to 40/10. 
Now, you can add 40/10 and 3/10. The result is 43/10.