Find the rule 2 / 5 4 / 7 8 / 11 16 / 19 and so on

Find the rule 2 / 5 4 / 7 8 / 11 16 / 19 and so on

=2^n/（3+2n）
It's the molecule: 2 to the nth power
Denominator 3 + 2n

According to the above rule, the nth number is

2n-3

After driving from Shanghai to Nanjing, the original plan was to arrive at 11:30 noon. But after starting, the speed increased by 17 and arrived at 11:00. The next day, I returned from Nanjing at the same time. After driving 120 kilometers according to the original plan, I increased the speed by 16 and arrived in Shanghai at 11:10. How many kilometers is the distance between the two places?

Suppose the original planned speed of the car is XKM, 11:30-11:00 = 30 minutes = 12 hours, 12 ^ [1 ^ (1 + 7)], = 12 ^ [1 ^ [8], = 12 ^ [18, = 4 (hours); 11:30-11:10 = 20 minutes = 13 hours & nbsp; 4x-120 = (4-120 ^ X-13) × (1 + 16) x, & nbsp; 4x-120 = (4-120x-13)