Đáp án:
Ta có: $\widehat{aAB}$ `=` $\widehat{x}$ `= 70^o` (hai góc đối đỉnh)
`+` $\widehat{x}$ `+` $\widehat{y}$ `= 180^o` (hai góc kề bù)
`⇔ 70^o +` $\widehat{y}$ `= 180^o`
`⇒` $\widehat{y}$ `= 180^o - 70^o = 110^o`
`+` $\widehat{B}$ `=` $\widehat{t}$ `= 80^o` (hai góc đối đỉnh)
`+` $\widehat{t}$ `+` $\widehat{z}$ `= 180^o` (hai góc kề bù)
`⇔ 80^o +` $\widehat{z}$ `= 180^o`
`⇒` $\widehat{z}$ `= 180^o - 80^o = 100^o`
Vậy $\widehat{x}$ `= 70^o`, $\widehat{y}$ `= 110^o`, $\widehat{t}$ `= 80^0`, $\widehat{z}$ `= 100^o`
