1. To find slope use the slope equation which would be (3 - -1)/ (5-3). The slope is m = 4\2 which is m = 2
2. Plug in one of the points to find the y-intercept. Using the point (5,3) , you would plug this point into the slope intercept equation, along with the slope which was found. 3= (2 x 5) +b. Solving this equation b=-7
40 I believe because the space of the auto mobile catching up to the train is 4 hours. 4 times 30 is 120 miles so u need to figure out a number that can reach 120 in three hours. 3 times 40 is 120