Respuesta :

Given the triangle is isosceles,

[tex]\begin{gathered} \angle A+\angle B+\angle C=180^{\circ} \\ 2\angle A+140^{\circ}=180^{\circ} \\ 2\angle A=180-140 \\ 2\angle A=40 \\ \angle A=\frac{40}{2} \\ \angle A=20^{\circ} \end{gathered}[/tex]

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