口算题.
11-9= 15-7= 12-8= 14-6= 18-9= 14-10=
11-6= 13-8= 15-9= 18-7= 16-9= 12-9=
14-7= 18-8= 13-9= 14-9= 17-7= 17-8=
11+12= 18-9= 18-10= 18+19= 2+8= 3+8=
14-1= 18-0= 11-6= 8+19= 16+3= 14-8=
11+0= 18+2= 3+11= 19+11= 2-0= 9-8=
15-14= 2+0= 14-6= 15-6= 11-1= 13-0=
11-9= 13+3= 11-10= 15-8= 15+9= 13-8=
7+13= 11+6= 7+6= 6+16= 12+9= 4+17=
10+7= 13+18= 14+2= 17-4=