`\text{Qua O kẻ d // a}`
`=>d////b(do` `a////b)`
`Ta` `có:` `a////d`
`=>\hat{A_1}=\hat{O_1}=36^o(\text{2 góc so le trong})`
`Do` `d////b`
`=>\hat{O_2}+\hat{B_1}=180^o(\text{2 góc trong cùng phía})`
`=>\hat{O_2}=180^o-\hat{B_1}=180^o-145^o=35^o`
`=>x=\hat{O_1}+\hat{O_2}=36^o +35^o=71^o`