$ABCD$ là hình thang
$→\widehat{A}+\widehat{D}=180^\circ$ (2 góc kề cạnh bên)
$→\widehat{B}+\widehat{C}=180^\circ$ (2 góc kề cạnh bên)
$\widehat{A}+\widehat{D}=180^\circ$
mà $\widehat{A}=1,5\widehat{D}$
$→1,5\widehat{D}+\widehat{D}=180^\circ$
$→2,5\widehat{D}=180^\circ$
$→\widehat{D}=72^\circ$
$→\widehat{A}=1,5.72^\circ=108^\circ$
$\widehat{B}+\widehat{C}=180^\circ$
mà $\widehat{B}-\widehat{C}=24^\circ$
$→\widehat{B}=(180^\circ+24^\circ):2=102^\circ$
$→\widehat{C}=(180^\circ-24^\circ):2=78^\circ$