Explanation:
by considering how many inches (") are in one foot (').
the answer is 12. there are 12 in in every ft.
so, now we can convert everything to the smallest scale (inches) and do the calculation based on inches :
(8×12 + 4) - (2×12 + 6) = 96 + 4 - 24 - 6 = 100 - 30 = 70"
and now to translate 70" back into ft and in :
70/12 = 5 with a remainder of 10
70" = 5' 10"