It is known that the area of trapezoid is 84 square centimeters, the upper bottom is 6cm, and the lower bottom is 15cm. Find the area of the shadow part of a large triangle More than one hour, invalid

It is known that the area of trapezoid is 84 square centimeters, the upper bottom is 6cm, and the lower bottom is 15cm. Find the area of the shadow part of a large triangle More than one hour, invalid

sixty