Ef is the median of trapezoid abcd.

Part A)

B) length of BC =  x + 12 =  x + 12 = 11 + 12 =23

length of EF =  4x - 18 =  4(11) - 18 = 44 - 18 =26

length of AD =  3x - 18 =  3(11) - 4 = 33 - 4 =29

Step-by-step explanation:

Median of trapezium is

In provided figure, base1 is x+12 and base2 is 3x-4

A) solve for value of x

calculate the median

B) To find the length of BC, AD and EF , put the value of x in equation of lines

length of BC =  x + 12 =  x + 12 = 11 + 12 =23

length of EF =  4x - 18 =  4(11) - 18 = 44 - 18 =26

length of AD =  3x - 4 =  3(11) - 4 = 33 - 4 =29

yes because there is exactly one y value for every x value

for function there can't be more than one value for every x value