X is the number of hours to burn 450 calories:
equality method:
600 calories * 1 hour = 450 calories * x hours
x hours = 450/600 calories * 1 hour
x = 0.75
So, she needs 0.75 hours (45 minutes) to burn 450 calories
Inequality method:
600x > 450
x > 450/600
x > 0.75
So, she needs at least 0.75 (45 minutes) to burn at least 450 calories.
Hope this Helps! :D