This may look a little confusing but all you have to do is plug the equation given for h(x) which is 2x-5 in to the h(x) area in the equation where it says h(x) + g(x).
So far that’s (2x-5) + g(x)
Then,
Do the same with equation given for g(x) which is now,
By definition, the average exchange rate is given by: Substituting values we have: Rewriting we have: Answer: the average change per year in teachers' salaries for the last fifty years is: