Mathew reads equal numbers of pages of a book every week. The graph shows the number of pages of the book left to read, y, after x weeks: A graph titled Mathew’s Book Reading shows Number of Weeks on the x-axis and Number of Pages Left on the y-axis. The scale on the x-axis shows numbers from 0 to 6 at increments of 1, and the scale on the y-axis shows numbers from 0 to 210 at increments of 30. A straight line joins the ordered pairs 0, 150 and 1, 120 and 2, 90 and 3, 60 and 4, 30 and 5, 0.

Which equation best models the relationship between x and y?

y = −30x + 150
y = −5x + 30
y = −30x + 210
y = −5x + 150