What is the sum of 4a^2 − 7a − 5 and −8a^2 − 2a + 7?

1. a music store marks up the instruments it sells by 30%. a. if the store bought a guitar for $45, what will be its store price? b. if the price tag on a trumpet says $104, how much did the store pay for it? c. if the store paid $75 for a clarinet and sold it for $100, did the store mark up the price by 30%?