[1+(5×7-2×15)]:2×(1×8-15):[3:(1+14:7)+2]=
[1+(35-2×15)]:2×(1×8-15):[3:(1+14:7)+2]=
[1+(35-30)]:2×(1×8-15):[3:(1+14:7)+2]=
(1+5):2×(1×8-15):[3:(1+14:7)+2]=
6:2×(1×8-15):[3:(1+14:7)+2]=
6:2×(8-15):[3:(1+14:7)+2]=
6:2×-7:[3:(1+14:7)+2]=
6:2×-7:[3:(1+14:7)+2]=
6:2×-7:[3:(1+2)+2]=
6:2×-7:(3:3+2)=
6:2×-7:(1+2)=
6:2×-7:3=
3×-7:3=
-21:3=
=-7
