You cannot add number which are in different units, so something has to be converted.

Let's convert #" " 33 # inches to feet and inches and then add.

#1 " foot " = 12 " inches"#

#33# inches = (24 + 9 ) inches = 2 feet and 9 inches (24+9)

#color(white)(xxxxx)"feet" color(white)(xx)"inches"#

#color(white)(xxxxxx)4 color(white)(xxxx)7#

#color(white)(xxx.x)ul(+2 color(white)(xxxx)9)#

#color(white)(xxxxxxx) color(white)(xxx)cancel16" "#add the inches first. It is more than 12!!

#color(white)(xxxxxx) ul(1color(white)(xxxx)4)" "# 16 inches to feet and inches. #(16 = 12+4)#

#color(white)(xxxxxx) 7color(white)(xxxx)4" "# now add the feet

Answer: #7 " feet " and 4 " inches "#