Which value if any pls help

For f(x)=2x+3 and g(x)=x^2- 8 find (f+g) (x)

Clarence wants to buy a new car. he finds an ad for a car that costs 27,200 dollars. suppose his local sales tax is 7%. -how much would he have to pay? -what is the cost of the car including tax? -if clarence has 29,864 saved, can he pay cash to buy the car?

In the equation sqrt(n+5)-sqrt(11-10)=1. what is the value of n