I don't understand what you have written- and probably your graphing sofware didn't either! You have h(t) on the left and "h*t" on the right. Is that h on the right the same as the h on the left? If so do you mean "t+ h(t)" or "t+ h(t)t"? Or is the h on the right simply a number? Obviously, no graphing software is going to accept the same name for a constant inside a function definition as you have given to the function itself!

If the h on the right really is the function h(t), you will need to solve for h so you do not have an h in the definition. Exactly how you do that depends on whether that is "t+ h(t)" or "t+ h(t)t".