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The perimeter of a right triangle is 144 cm. The base is 12 cm. less than the adjacent. Find the area.
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The person who posted it, simply does not know the terminology.
Concretely, he does not know that the perpendicular sides of a right-angled triangle are called the legs.
It is the source of difficulties that some tutors have trying to find the sense, hidden behind wrong terminology usage.
The correct formulation of the problem is THIS:
The perimeter of a right triangle is 144 cm. One leg is 12 cm shorter than another. Find the area.
In this formulation (in this interpretation) the problem was solved under this link
https://www.algebra.com/algebra/homework/Systems-of-equations/Systems-of-equations.faq.question.1108259.html
https://www.algebra.com/algebra/homework/Systems-of-equations/Systems-of-equations.faq.question.1108259.html
But the original formulation in the post #1108259 was wrong again, and I pointed to it to the author of the post.