If h(x) is the inverse of f(x), what is the value of h(f(x))

For the rule of 78, for a 12-month period, the last term in the sequence is 12 and the series sums to 78. for an 10 month period, the last term is and the series sum is . for a 15 month period, the last term is and the series sum is . for a 20 month period, the last term is and the series sum is

If i have 20$ and i gave 5$ away how much i got

Does anyone know how to solve and graph this: 4 + | a + 2 | < 7the only part i don't get is the "4 +"