Question 116201
ONE APPROACH WOULD BE TO CONVERT EVERYTHING TO INCHES AND THEN CONVERT BACK:

8FT 4IN =96+4=100 IN

2FT 9IN =24+9=33IN

100 IN -33 IN=67 IN 

67/12 =5 FT 7 IN

Another way

8ft 4 in=7ft 16 in minus 2 ft 9 in =5ft 7 in

Hope this helps---ptaylor