Vì AB//CD(gt)
=>\(\widehat{B}+\widehat{C}=180\)
hay: \(3\widehat{C}+\widehat{C}=180\Rightarrow4\widehat{C}=180\Rightarrow\widehat{C}=45\)
=>\(\widehat{B}=3\cdot\widehat{C}=3\cdot45=135\)
Có: \(\widehat{A}-\widehat{C}=40\Rightarrow\widehat{A}=40+\widehat{C}=40+45=85\)
Vì AB//CD(gt)
=>\(\widehat{A}+\widehat{D}=180\Rightarrow\widehat{D}=180-\widehat{A}=180-85=95\)