Remember that the area of a rectangle is length times width; since we don't know the width, we'll use the Pythagorean theorem to find it first:
![l= \sqrt{h^(2)-c^(2) }](https://img.qammunity.org/2019/formulas/mathematics/middle-school/5n6kkmggt27br8762daj3j1gyy6yk9fyyv.png)
Where l is the leg, and h the hypotenuse. We know that one of the legs, the base has a measures 34.3 inches and the hypotenuse a measures 42.1 inches.
Replace the values to get:
![l= \sqrt{42.1^(2)-34.3^(2) }](https://img.qammunity.org/2019/formulas/mathematics/middle-school/ef1asn343ta0ahtryvslmlz43gz7bo8b54.png)
![l=24.4=w](https://img.qammunity.org/2019/formulas/mathematics/middle-school/3cgr458zm623309z41woamvbyh9uug597k.png)
Now that we know the width (w), we just net to multiply it by the length to get our area:
![A=(24.4)(34.3)=836.9](https://img.qammunity.org/2019/formulas/mathematics/middle-school/k9s1a0g7h1bioly2np5buudrmpkk037a61.png)
We can conclude that the correct answer is
B) 836.9 in.