Meee..i have no idea how to do these

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for #1 do 9x-4=42 then once you solve that you’ll find what x is and then you use the answer that you get for x and plug it into 9x-4 once you find that you do that angle plus 42 and subtract that answer from 180 since all triangles equal 180. when you find the 3rd angle you subtract it from 180 because the 3rd angle and exterior angle together equal 180 because they’re a linear pair so then you’ll get your exterior angle! hope this helped :)