Both triangles DEF and HIJ are similar, and they are placed in such a way that their hypotenuses are aligned in the same line. This means that the slope of DE and the slope of HI are the same.
To calculate said slope, you can use the following formula
Where
(x₁, y₁) are the coordinates of one point of the line
(x₂, y₂) are the coordinates of another point of the line.
Using D(8, 32) and E(12,24) you can calculate the slope as:
The slope of DE and HI is m=-2