21/8*(6/7-2/3)
a*(b-c) = ab - ac
21/8*6/7 - 21/8*2/3 = 126/56 - 42/24 = 378/168 - 294/168 = 84/168 = 1/2
21/8*(6/7-2/3)
a*(b-c) = ab - ac
21/8*6/7 - 21/8*2/3 = 126/56 - 42/24 = 378/168 - 294/168 = 84/168 = 1/2