14. Wouldn't the two equations both be equal to each other due to congruent triangles?
17. Wouldn't AB and CB be equal to each other since a perpendicular bisector separates the triangle into two equal parts?
19. EF is a midsegment. A midsegment is half the measurement of the bottom side. For example (answers your question): EF = 8. A midsegment is a segment that connects two midpoints of a figure together. The equation for a triangle's midsegment is 1/2(x).