F (x+h) = Given: F (x) = 2x + 3, find and simplify.

Something's not quite write about your problem statement. I think you meant the following:

Given F (x) = 2x + 3, find and simplify F (x+h).

F (x+h) = 2 (x+h) + 3 = 2x + 2h + 3.

I'd say you could come out equally well by leaving your result as

F (x+h) = 2 (x+h) + 3

or by removing the parentheses: 2x + 2h + 3