The smaller sides a = 3 and b = 4 add to a+b = 3+4 = 7 which does NOT exceed the third side c = 7.
Therefore, a+b > c is not true and a triangle cannot be formed. The sum of any two sides of a triangle must exceed the third side. Refer to the triangle inequality theorem for more information.
Since a triangle cannot be constructed with those side lengths, this means we'll have 0's for each of the boxes.
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If your teacher made a typo and didn't mean to use those numbers, then let me know and I'll update my solution.
