Slope=(difference of y coords)/(difference of x coords)=
(17-7)/(-15-(-16))=10/(-15+16)=10.
Slope is 10.
If you draw a graph picture it will make more sense. Draw a right triangle where the vertical leg is made from the y coords and the horizontal leg from the x coords. The lengths of the legs are just the distances between the coordinates as measured vertically (y) and horizontally (x). If the hypotenuse leans to the right, the slope is positive, and if it leans to the left it's negative. The slope is just a ratio so it's also the tangent of the angle at the base of the triangle. The length of the hypotenuse can be found using Pythagoras' Theorem, and it's the straight line distance between the two points.