Is -2 a constant or linear monomial

Which values for a and b will create infinitely many solutions for this system of equations? ax-y=8 2x+y=b

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

The scatterplot below shows the number of hours that students read weekly and the number of hours that they spend on chores weekly. which statement about the scatterplot is true?