3/4一8/4(8.6)÷2.9x3%6=o丶89
3/4-括号3/8+1/4=3/4-1/4-3/8=2/4-3/8=4/8-3/8=1/8
3/4-(3/8+1/4)=6/8-(3/8+2/8)=6/8-5/8=1/8