Решить подробно 5/7*(21/20-7/30)+16/21: 8/7 и ещё вот (1-1/2): (1/3-1/4)*(1/6)

А)=5/7(63/60-14/60)+16/21×7/8=
=5/7×49/60+2/3=7/12+2/3=7/12+8/12=15/12=
=5/4=1 1/4

б)=1/2÷(4/12-3/12)×1/6=1/2÷1/12×1/6=
=1/2×12/1×1/6=1