giúp mk vs gấpppppppppppppp

Xét tứ giác `ABCD`, ta có `:`

  $\widehat{A}$ `+` $\widehat{B}$ `+` $\widehat{C}$ `+` $\widehat{D}$ `=` $360^0$ `(` tổng `4` góc trong tứ giác `)`

  $120^0$ `+` $90^0$ `+` $\widehat{C}$ `+` $\widehat{D}$ `=` $360^0$

                                        $\widehat{C}$ `+`$\widehat{D}$ `=` $360^0$ `-` $120^0$ `-` $90^0$

                                        $\widehat{C}$ `+` $\widehat{D}$ `=` $150^0$

Ta có `:` $\widehat{C}$ `=` `2`$\widehat{D}$ `(cmt)`

      mà $\widehat{C}$ `+` $\widehat{D}$ `=` $150^0$ ( gt )

`=>` $\widehat{D}$ `+` `2`$\widehat{D}$ `=` $150^0$

`=>` `3`$\widehat{D}$ `=` $150^0$

`=>` $\widehat{D}$ `=` $150^0$ `: 3`

`=>` $\widehat{D}$  `=` $50^0$

Ta có `:` $\widehat{D}$ `+` $\widehat{C}$ `=` $150^0$ `( cmt )`

              $50^0$ `+` $\widehat{C}$ `=` $150^0$

                                $\widehat{C}$ `=` $150^0$ `-` $50^0$

                                $\widehat{C}$ `=` $100^0$

Vậy $\widehat{D}$ `=` $50^0$

        $\widehat{C}$ `=` $100^0$

`#TN`