Nevernevergiveup
Source: Veritas prep
Andy and Frank start out at opposite ends of a 450-mile route, cycling toward each other at their respective constant rates. Frank cycles at 15 miles per hour and Andy cycles at 25 miles per hour. If Andy leaves at 6am and Frank leaves at some point after that, which combination below represents a time at which Frank begins his ride and a time at which the two will meet along the route?

Solution
For a question like this, it can be helpful to set up your own grid, noting the times that Frank can leave, the distance Andy will have traveled at that point,the distance they'll need to cover together, and the time at which they'll have covered that distance (working at their combined rate of 40 miles per hour):
Frank Leaves.....Andy Has Traveled......Distance Remaining....Time They Meet
8am..........50 miles.....400 miles......6:00pm
10am........100 miles......350 miles.......6:45
12pm........150 miles......300 miles......7:30
This row is reflected in two answer choices, so it's the correct pairing of 12pm and 7:30pm.
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Here is a better solution. IR questions are usually time consuming if you dont know where to start.
Let t be the time after which Andy and Frank meet and x be the number of hours AFTER 't', when Frank starts.
Thus, per the question,
15*(t-x)+25*t = 450 ---> t = (90+3x)/8, realize that the options given are either complete hours or half hours.
Thus, the value of x will be such that it gives a value of t as a.0 or a.5 hours (i.e. divisible by 4 but NOT by 8).
Use the options to see what values of x you need,
Start with x= 2 (for 8 am), x = 3 for 9 am, x= 4 for 10 am , x = 6 for 12 PM etc.
You will see that when x =6 (i.e. Frank starts at 6 AM+ 6 hours = 12 PM), t = 13.5 hours from 6 am --> 7:30 PM.
Thus, your values are 12 PM and 7:30 PM.
Hope this helps.