big trapezoid: upper base = 4 cm ; lower base = 12cm ; side = 10cm
small trapezoid: upper base = y ; lower base = ? ; side = 3cm
Figure ABCD is contracted into figure KLMN, this means that they have the same proportion as to the other sides of the figure.
side: 10 cm / 3cm = 3.33
upper base: 4cm / 3.33 = 1.20 value of y.
lower base: 12cm / 3.33 = 3.60
4/10 = 0.40 ; 1.20/3 = 0.40
4/12 = 0.33 ; 1.20/3.6 = 0.33
10/12 = 0.83; 3/3.60 = 0.833
