First we need to add the time she takes warming and the time she takes going to the the gym:
[tex]15minutes+40minutes=45minutes[/tex]
Next, we area going to subtract those 45 minutes from the time the game begins:
[tex]6:45pm-45minutes=6:00pm[/tex]
We can conclude that she should leaver her house at 6:00 pm if she wants to get in time for her 6:45 pm game.