Упростите числовое выражение а 6:(1/2+1/2);б12:(1/2+1/2+1/2+1/2);в(1/5+1/5+1/5)•1/3;г(2/7+2/7+2/7+2/7)•21/8

6:(1/2+1/2)=6:2/2=6:1=612:(1/2+1/2+1/2+1/2)=12:4/2=12:2=6(1/5+1/5+1/5)*1/3=3/5*1/3=1/5(2/7+2/7+2/7+2/7)*2 1/8=8/7*9/8=9/7=1 2/7