1/6*(12/17b-18/23c) = (1/6)(12/17b) - (1/6)(18/23c)= 2/17b - 3/23c
1 3/4*(4a + 16/21b - 2 2/3) = (7/4)(4a) + (7/4)(16/21b) - (7/4)(8/3)= 7a + 28/3b - 14/3
1/6*(12/17b-18/23c) = (1/6)(12/17b) - (1/6)(18/23c)
= 2/17b - 3/23c
1 3/4*(4a + 16/21b - 2 2/3) = (7/4)(4a) + (7/4)(16/21b) - (7/4)(8/3)
= 7a + 28/3b - 14/3