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From the diagram the angles are .

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In a triangle sum of angles are .

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      (Remove the brackets)

                      (Add: )

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    (Add 18 to each side)

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               (Apply addiitve inverse propetry: )

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                     (Apply addiitve identity propetry: )

                              (Subtract: )

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                          (Divide each side by 6)

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                               (Cancel common terms)

So, the angle measures are  .

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The value of x is . The angle measures are  . 

is an acute angle. So, the triangle is acute triangle.