<em>1. 348:4=87;</em>
<em>2. 87*6=522;</em>
<em>3. 400-522=-122.</em>
4/8-1/8=3/8
4+8=12
Как то так
(9*2+5/9-21*1+20/21):49*1+8/49+9*1+8/9:6=(23/9-41/21):57/49+17/9:6=(7*23/63-3*41/63):57/49+17/9:6=(161/63-123/63):57/49+102/9=38/63:57/49+102/9=38*49/63*57+102/9=1862/3591+102/9
=1862+399*102/3591=42560/3591=12целых468/3591