No.1.
15+18=33 minutes 200 * 15 = 3000 miles
3000/75= 40 minutes
40-33=7 minutes
No.2.
1 ／ 2 x = 1 ／ 3 y
2 x = 3 y
x／y = 3／2
长蜡烛的长度是短蜡烛的3/2
No.3.
45x - 60 ( x-0.5 ) = 8
45 x - 60 x +30 = 8
45 x - 60 x = -22
-15 x = -22
x= 22 ／ 15 hour
22 ／ 15 ＊ 45 ＝ 66 km
60km / 45 = 12/7 hour
68km / 60 +0.5 = 23.5 / 15 hour
－23.5 / 15 + 12 / 7 = 15.5 / 105 = 8.86 minutes (2dp)
应该距离 66 km 于城市甲.10 km一个小站,故提前为60 km .慢车至少要等8.86分钟（四
舍五入2位小数）.