The working is correct, BUT, they did not substitute their x values in which they have found into one of the equations to determine the y values. By using x = 3 and x = -2, sub them into equation 2 (mainly since it is simpler),
x = 3,                 x = -2
y = 4x + 1Â Â Â Â Â Â Â Â Â Â Â Â Â Â y = 4x + 1
  = 4(3) + 1              = 4(-2) + 1
  = 13                  = -7
Therefore, the correct points of intersection are (3 , 13) and (-2 , -7)
Hope this helped!