Ta có: \(\widehat{xAy}=\widehat{x'Ay'}\) (đối đỉnh)
\(\Rightarrow\widehat{xAy}=\widehat{x'Ay'}=\frac{\widehat{xAy}+\widehat{x'Ay'}}{2}=\frac{140^0}{2}=70^0\)
Có: \(\widehat{xAy}+\widehat{x'Ay}=180^0\left(kề-bù\right)\)
\(\Rightarrow\widehat{x'Ay}=180^0-\widehat{xAy}=180^0-70^0=110^0\)