Answer:
[tex]225\:\text{minutes}[/tex]
Step-by-step explanation:
To navigate through this problem, start by finding how much each senator can complete in a fixed amount of time. I'll choose 10 as it's the greatest common factor of 30 and 50.
In 10 minutes, the junior senator can complete [tex]\frac{10}{50}=\frac{1}{5}[/tex] of the labyrinth.
In 10 minutes, the senior senator can complete [tex]\frac{10}{30}=\frac{1}{3}[/tex] of the labyrinth.
Therefore, working together, they can complete [tex]\frac{1}{5}+\frac{1}{3}=\frac{8}{15}[/tex] of the labyrinth in 10 minutes. Thus, it will take them [tex]\frac{15}{8}\cdot 10 \text{ minutes}=18.75\:\text{minutes}[/tex] to complete one labyrinth.
The amount of time it take them to complete 12 labyrinths is then [tex]18.75\cdot 12 =\boxed{225\:\text{minutes}}[/tex]
