口算算术
1.90-9=24-10-7=
46+5=20+13-9=
8+57=34+(25+5)=
98-70=58-(58-8)=
65+20=39+7-20=
2.25+7=50-8=
86-5=4+65=
20+67=42+30=
73-40=85-7=
8+45=76-60=