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Check Attachment!!!
According to the statement of the question, we have:
a/b = 3/4
Note that according to the attached figure, b > a, then the correct proportion will be a to 3, as well as b to 4, because b > a and 4 > 3
Isolating a and b:
a = 3b/4
b = 4a/3
From Pythagoras:
h² = a² + b² - as a = 3b/4 and b = 4a/3, so
b = 4h/5
a = 6h/5
For Area:
A = b.a/2
as b = 4h/5 and a = 6h/5, so
A = 12h/25