Ricardo has r minutes left on his cell-phone card. He wants to call his friend and still have 8 minutes left over to make calls later. Which expression describes the length of time he can talk to his friend?
A. 8 – r
B. 8r
C. r + 8
D. r – 8

Which of the following represents a number squared is equal to twenty more than nine times that number ? a) x squared = 9x + 20 b) x squared = 20x + 9 c) x squared > 9 + 20x d) x squared = 9 + x + 20

How do i do this activity, is appreciated

Expresa commuter train leaves downtown sation and travels at a average speed of 55 miles per hour towards the north side sation, which is 50miles away. thirty minutes later, express commuter train #7 leaves north side and travels at a average speed of 35miles per hour towards downtown sation. at the moment the two trains pass each other, how far(in miles) is train #12 from the downtown sation and how long(in minutes) has the #12 train been traveling