Answer:
You must wait 60 minutes for all three lines to arrive at Union Station at the same time again.
Step-by-step explanation:
The complete question in the attached figure
Step 1
Find the least common multiple (LCM) of the three numbers
List the prime factors of each number
[tex]10=(2)(5)\\12=(2^2)(3)\\15=(3)(5)[/tex]
Multiply each factor the greatest number of times it occurs in any of the numbers to find out the LCM
The LCM is equal to
[tex](2^2)(3)(5)=60[/tex]
therefore
You must wait 60 minutes for all three lines to arrive at Union Station at the same time again.