(100-64-15):7*(5+9:3)-2*(8-2*2)=b
21:7*8-2*4=b
3*8-8=b
24-8=b
b=16
(231-6*9+3*8)-(8*9+7*4):10=c
(231-54+24)-(72+28):10=c
201-100:10=c
201-10=c
c=191
27:(6*5-3*9):3*(9:9+8:4*3:6*14:7:2)=a
27:(30-27):3*(1+2*3:6*14:7:2)=a
27:3:3*(1+6:6*14:7:2)=a
9:3*(1+1*14:7:2)=a
3*(1+14:7:2)=a
3*(1+2:2)=a
3*2=a
a=6