1. 1.1. An online electric scooter rental service charges a fixed amount for a ride and a certain amount for each minute of rental. Katya paid 78 rubles for a ride lasting 3 minutes. Lena paid 108 rubles for a ride lasting 8 minutes. It takes Kolya 5 minutes to get from home to work. How much will he pay for this ride?
Answer: 90.

## Solution.

1st method. If the rental of a scooter costs $x$ rubles, and a minute of use costs $y$ rubles, then $x+3y=78$, and $x+8y=108$. Solving this system, we get that $y=6, x=60$. Then Kolya will pay $60+30=90$ rubles.

2nd method. Notice that Lena's trip is 30 rubles more expensive than Katya's trip and lasts 5 minutes longer. It turns out that 1 minute, not counting the rental cost, is $30:5=6$ rubles. Then, since Katya paid 78 rubles for 3 minutes, $78-3 \times 6=60$ rubles. Therefore, Kolya paid $60+30=90$ rubles.