Question 891730
Whew!  That's a convoluted problem, isn't it?
15 hours a week, with no more than 3 running.
Since running burns the most calories, she'll want to maximize that.
3 hours running at 531 cal = 1593 calories
That leaves 12 hours.  Even though walking is the lowest calorie burner, she wants to walk 2x as often as biking.  We'll want the minimum number of hours of walking in order to maximize calories.
12 = B + 2B (twice as many walking hours as biking)
12 = 3B
4 = B
4 hours biking * 472 cal = 1888 calories
If there are 4 hours biking, the minimum walking is 8 hours 
8 hours walking * 354 cal = 2832 calories
.
Total:
3 hours running at 531 cal = 1593 calories
4 hours biking * 472 cal = 1888 calories
8 hours walking * 354 cal = 2832 calories
Maximum amount of calories = 6313 calories in 15 hours