Jacob bought postcards on a trip. He sent 5 cards to his aunt. He sent half of the remaining cards to his sister. He sent one to a friend and had 4 left. How many postcards did Jacob buy?

Use the inverse of the function y=x^2-18x to find the unknown value [tex]y = \sqrt{bx + c \: + d} [/tex]

Rachel reads 1/5 of the pages of a book plus 12 pages on the first day. on the second day, she reads 1/4 of the remaining pages plus 15 pages. on the third day, she reads 1/3 of the remaining pages plus 18 pages. on the fourth day, she reads the remaining 70 pages. how many total pages are in the book?

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