Mrs. Lewis has placemats that are in the shape of trapezoids. She knows that the perimeter of each one is 50 inches. She also knows the length of three sides: 12 inches, 12 inches, and 15 inches. What is the length of the fourth side? Enter your answer in the box.

The figure shows triangle def and line segment bc, which is parallel to ef: triangle def has a point b on side de and point c on side df. the line bc is parallel to the line ef. part a: is triangle def similar to triangle dbc? explain using what you know about triangle similarity. part b: which line segment on triangle dbc corresponds to line segment ef? explain your answer. part c: which angle on triangle dbc corresponds to angle f? explain your answer. asap