Step-by-step explanation:
AD ≅ BC, Given
∠BCD ≅ ∠ADC, Given
CD ≅ CD, Reflexive property
ΔBCD ≅ ΔADC, SAS congruence
∠BDC ≅ ∠ACD, CPCTC
ΔECD is an isosceles triangle, definition of isosceles
DE ≅ CE, properties of isosceles triangles
Answer by JKismyhusbandbae: The mean is the average of all the numbers. You add all the numbers and divide by how many numbers you added to get the mean.
