Question 550573
Length of the midsegment of a trapezoid is the average length of the bases,

i.e. LM = (AB+DC)/2

Substituting the values given, we get

4x+3 = ((x+8)+187))/2

Multiplying both sides by 2 ...
> 2*(4x+3) = ((x+8)+187))
> 8x+6 = x+195
> 8x-x = 195-6
> 7x = 189
> x = 27 ( Dividing both sides by 7)