11-6 2/3-3 5/7 решите плиз я даун

11-6 2/3-3 5/7=11-6 14/21-3 15/21=10 21/21-(6 14/21+3 15/21)==10 21/21-9 29/21=10 21/21-10 8/21=13/21

(231-140-78)/21 = 13/21