Problem 8
Notice how the smaller two sides add up to 21+25 = 46 but this is not larger than the third side 48
For a triangle to be possible, we must be able to add up any two sides and have the sum be larger than the third side. This is the triangle inequality theorem.
So that's why this current triangle is not possible.
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Problem 9
Let's find angle b
b+125 = 180
b = 180-125
b = 55
Now we'll use this to find angle 'a'
a+b+130 = 180
a+55+130 = 180
a+185 = 180
a = 180-185
a = -5
We can't have negative angle values, so such a drawing isn't possible.