Bonjour,
A. 1/7×8/3+2/7 = 8/21+2/7 = 8/21+6/21 = 14/21 = 2/3
B. 7/5+3/5×11/6 = 7/5+33/30 = 42/30+33/30 = 75/30 = 15/6
C. 10/3-2×(13+1)/(13-1) = 10/3-2×14/12 = 10/3-2×7/6 = 10/3-14/6 = 10/3-7/3 = 3/3 = 1
D.5/6-7/6×1/14+2/3 = 5/6-7/84+2/3 = 10/12-1/12+8/12 = 17/12