Answer :
He can find the area of the individual shapes the backyard is made up of, then take the sum.
Area of composite figure
A composite figure is made up of different shapes and hence their area might be difficult to determine.
In order to determine the area of such a complex shape, the area of the individual shapes is first determined and then sum up. The sum of their areas will give the area of the composite figure
For your neighbour, he can find the area of the individual shapes the backyard is made up of, then take the sum.
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