Draw a diagram to illustrate the problem as shown below.
The area of triangle acb is
A₁ = (1/2)*20*h = 10h
The area of trapezoid abcd is
A₂ = (1/2)*(20+12)*h = 16h
The ratio A₁/A₂ is
A₁/A₂ = (10h)/(16) = 5/8
Answer:
The ratio of triangle acb to the area of trapezoid abcd is 5/8.