A Family has built a fence around three sides of their property. In total, they used 550 feet of fencing. By their calculations, the lot is one acre (43,560 square feet). Is this correct? Explain your reasoning.

My teacher gave me a hint and told me that it is a trapezoid land. and the area of the trapezoid is
A=1/2(b1+b2)h

and she gave me additional details:
A=1/2x[x+(550-2x)=43,560

and i still don't know how to solve this.. please show your work :(

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