Hey there! :)
Area of triangles → (base × height) ÷ 2
The base and height are the 2 legs. You have to find the length of the other leg to find the area, using the Pythagorean Theorem.
a² + b² = c² → c² - a² = b²
c = 12
12² = 12 × 12 = 144
a = 10
10² = 10 × 10 = 100
144 - 100 = 44
√44 = 6.6
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Area of triangles → (base × height) ÷ 2
Base: 10
Height: 6.6
6.6 × 10 = 66
66 ÷ 2 = 33
The area is 33
Hope this helps :)