Answer:
scale factor = 7/8
Explanation:
Find a pair of corresponding sides that you know both lengths. Divide the second length by the first length.
The triangles are similar, and you are told that triangle ABC is similar to triangle DEF. From that statement you see that sides AB and DE are corresponding.
scale factor = DE/AB
scale factor = 28/32
scale factor = 7/8
The scale factor is 7/8, sop if you multiply the length of any side of triangle ABC by 7/8, you get the length of the corresponding side in triangle DEF.
Side BC corresponds to side EF.
BC = 20
EF = BC * 7/8
EF = 20 * 7/8
EF = 17.5
x = EF = 17.5