口算。9{1z3T1g5^2w'B;h
9+7=:~)}-V,Z(L;u5[5R9{1z3T1g5^2w'B;h
16-9=2B0v5x'o-[8p-r4K/d3G9{1z3T1g5^2w'B;h
8+9=(C,U3E*{2t7]9{1z3T1g5^2w'B;h
17-9=4w/[4f-g1R9W2I/n)Y/y9{1z3T1g5^2w'B;h