We know that the 2 triangles are proportional and are similar so that means there must be a scale factor between the sides of the triangles. To find the D, we need to use the scale factor and multiply it by CD to find DE. The scale factor can be found by dividing 2 similar sides so: EF divided by DG is 5/1.25 which is 4. We can then multiply the scale factor which is 4 by CD so: 3.25 * 4 is 13. DE = 13
