Slope is found by dividing the difference of the y-coordinates of two points on a line by the difference of the x-coordinates of those same two points.
Or in other words, it is defined as the ratio of the vertical change between two points to the horizontal change between the same two points.
Trial and error until I got to 75 x 104 and 60 x 128 (which abides by the fact that there has to be 24 more red boxes) which equals 7800 and 7680 and if you take them away from each other you get 120
