Can anyone also help me solve this and explain?

Plz ( true - false) all triangles have interior angles whose measure sum to 90.

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

Juanita wade's new car has an msrp of $28,902.11 including title and processing fees. the premier package which includes surround sound and dvd player costs three times the amount of the in-style package which includes leather seats and select wheels. the total cost of her new car was $34,290.08 which included the 6.5% sales tax. find the cost of the premier package to the nearest cent.