Solution:
As we given that
then using this conversion factor we can write 
and further it can be written as

Hence the required conversion factor is 2.54 cm/1 inch as we can see from the above calculation.
The answer: Dustin spent $66
$52+$49=$101
$101-$35=$66
Since inches are out of 12 this would be
4 ft - 1 ft = 3 ft
3' 1" - 1 " = 3 '
3 feet is also 2 ft and 12 inches
2' 12" - 9 " = 2' 3"
So the answer is 2 feet and 3 inches
Hope this helps
-GoldenWolfX