mph, and how many miles they are apart

Question

joyce left a reasturant and travled at 35 mph. an hour later, kevin left the same reasturant and traveled at 45 mph in the oppostire direction. how long has kevin travled when they are 400 miles apart? 

Answer 1

How long does Kevin travel? We don't know. So let's say his travel time is  x  hours. Joyce leaves an hour early, so let's say her travel time  (x + 1) hours. Because they are driving in opposite directions, we can add their travel distances to determine how far apart they are. How do we calculate their travel distances. Is there a variable in our equation? Can we solve our equation for the variable(s), if it or they exist?

Can you handle the rest of the solution? Try it.