2. To walk 2 km, ride 3 km on a bicycle, and drive 20 km by car, Uncle Vanya needs 1 hour 6 minutes. If he needs to walk 5 km, ride 8 km on a bicycle, and drive 30 km by car, it will take him 2 hours 24 minutes. How much time will Uncle Vanya need to walk 4 km, ride 5 km on a bicycle, and drive 80 km by car?
# Answer: 2 hours 54 minutes. (2.9 hours.)

## Solution:

Let $\frac{1}{x}, \frac{1}{y}, \frac{1}{z}$ be the walking speed, cycling speed, and driving speed, respectively. Then, according to the problem, we can set up the system:

$$
\left\{\begin{array} { c } 
{ 2 x + 3 y + 2 0 z = 6 6 } \\
{ 5 x + 8 y + 3 0 z = 1 4 4 . }
\end{array} \Rightarrow \left\{\begin{array} { c } 
{ 2 x + 3 y = 6 6 - 2 0 z } \\
{ 5 x + 8 y = 1 4 4 - 3 0 z }
\end{array} \Rightarrow \left\{\begin{array}{l}
x=96-70 z \\
y=40 z-42
\end{array}\right.\right.\right.
$$

Therefore, $4 x+5 y+80 z=4(96-70 z)+5(40 z-42)+80 z=174$ minutes. 174 minutes $=2$ hours 54 minutes.