How do you simplify 10h + 6 - 5h + 3?

First, change the subtraction sign to addition.

10h + 6 + (-5h) + 3

Then combine like terms. Terms with variables and terms without.

5h + 9 is the simplest form.

10h + 6 - 5h + 3

Combine like terms

5h + 9

And that's the answer.

You might be asking what is like terms. Like terms are terms that are the same "type". Like 3x and 4x are like terms. They both have those x's.