12/5+3/4×2-5/6=12/5+3/2-5/6=24/10+15/10-5/6=39/10-5/6=3+27/30-25/30=3+2/30=3+1/15=3又15分之1
12/5+3/4×2-5/6=12/5+3/2-5/6=72/30+45/30-25/30=92/30
12/5+3/2-5/6=12/5+9/6-5/6=12/5+2/3=36/15+10/15=46/15