Area of triangle 12Cm 7Cm 10Cm?

90 centimeters

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That is so wrong!

Let the three sides be a, b and c and let s = (a+b+c)/2

then area = sqrt[s*(s-a)*(s-b)*(s-c)]

So here s = 14.5 cm and so area = sqrt(14.5*2.5*7.5*4.5) = sqrt(1223.4375)

= 34.98 sq cm (to 2 dp)