(1/6+3/14):(5/21-1/14)

(1/6 + 3/14) : (5/21 - 1/14) = 2 2/7
1) 1/6 + 3/14 = 7/42 + 9/42 = 16/42 = 8/21
2) 5/21 - 1/14 = 10/42 - 3/42 = 7/42 = 1/6
3) 8/21 : 1/6 = 8/21 * 6 = 16/7 = 2 2/7