W*f is 4 1/2+2 2/3+3 1/4+2 1/2???
write different:
(4 1/2 + 2 1/2) + 2 2/3 + 3 1/4
= (7 + 2 2/3) + 3 1/4
= 9 2/3 + 3 1/4 -> can be written as 9 8/12 + 3 3/12
= 12 11/12
