设从三点过了x分钟,则有(`代表度的符号)：
1 重合时
(360/60)x=(360/720)x+45`
6x=0.5x+45`
5.5x=45`
x=90/11
2 成平角时
(360/60)x+[(360/12)`-(360/720)x]=180`
6x+30`-0.5x=180`
5.5x=150`
x=300/11
3 成直角时
(360/60)x+[(360/12)`-(360/720)x]=90`
6x+30`-0.5x=90`
5.5x=60`
x=120/11
以人格担保,绝对正确,快给分吧!