Express 243 as power of 3 explain

If f(x) = x+8 and g(x) = 4x- 3, find (f+g)(x)

Me because i don't understand how to do it.: )

The amount of tears in the room (denoted by ttt) can be defined as a function of the number of people present in the room (denoted by ppp), the number of chopped onions in the room (denoted by ooo), and the deliciousness of the onions (denoted by ddd) using this formula: t =3\cdot \dfrac{p\cdot o^3}{d^2}t=3? d 2 p? o 3 ?