Explanation:
1 pound is equivalent to 3500 calories.
if you burn 450 more calories per day, it will take as many days as the times 450 fits into 3500 :
3500 / 450 = 7.77777777... days
for 10 pounds we need to burn 10×3500 = 35000 calories.
35000 / 450 = 77.77777777... days (10 times more logically than for 1 pound).