Prove: The median of a trapezoid equals half the sum of its bases.(fill in the blanks of the equation in the second picture with the correct number/letter/sign based off the first picture.)

M(d/2, c/2)
N=((a+b )/, c / 2)
MN= (a +b)/2 - d/2) = (a+b-d)/2
AB=a
CD=b-d
MN=1/2 *(a+b-d)
I think it should be like this