Gerald purchased 55 paving stones to use in his garden. The graph shows points representing the number of stones left to place at several different times while Gerald is working. The three points are (0,55), (3,40) and (7, 20). complete the equation, in standard form, that represents the relationship between the number of paving stones left to place, y, and the time, x, Gerald has spent working.
And I got 5x+y=55