How to do this equation x=7-y

Pls! does anybody know a shortcut for answering these types of questions in the future?

Atotal of 766 tickets were sold for the school play. they were either adult tickets or student tickets. there were 66 more student tickets sold than adult tickets. how many adult tickets were sold?

Bo is buying a board game that usually costs bb dollars. the game is on sale, and the price has been reduced by 18\%18%. which of the following expressions could represent how much bo pays for the game? choose 2 answers: choose 2 answers: (choice a) a 0.82b0.82b (choice b) b 1.18b1.18b (choice c) c b-0.18b−0.18 (choice d) d b-18b−18 (choice e) e b-0.18bb−0.18b