#9 what is the answer

The triangles ABC and EDC have corresponding sides
The triangles ABC and EDC are similar
The given parameters are:
ED = 8, DC = 10, EC = 12, AB = 12
BC = 15 and AC = 21
To determine that the triangles are similar, we simply divide the corresponding sides to determine the scale factor (k).
So, have:
k = AB/ED = BC/DC
This gives
k = 12/8 = 15/10
Evaluate the quotients
k = 1.5 = 1.5
The scale factors are equal
Hence, the triangles ABC and EDC are similar
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