能简算的要简算.12-2÷7-5/7
=12-（2/7+5/7）
=12-1
=11;
4.2*25%+4/5*1/4
=0.24×(4.2+0.8)
=0.24×5
=1.2;
36÷[0.5*（7.5-0.7）]
=36÷[0.5×6.8]
=36÷3.4
=360/34
=180/17;
1/5+1.2*（3/4-7/12） 高人求教!
=1/5+0.9-0.7
=0.2+0.2
=0.4;
如果本题有什么不明白可以追问,