400+480:4+[68:2+4×(20+12+18)]=
400+120+(34+4×50)=
520+(34+200)=
520+234=754
[1+(5×7-2×15)]:2×(2×8-15):[3:(1+14:7)+2]=
[1+(35-30)]:2×(16-15):[3:(1+2)+2]=
(1+5):2×1:(3:3+2)=
6:2:(1+2)=
3:3=1
98+8×[1004-4×(8:2×2-4:4×2)]=
98+8×[1004-4×(4×2-1×2)]=
98+8×[1004-4×(8-2)]=
98+8×(1004-4×6)=
98+8×(1004-24)=
98+8x980=
98+7840=7938