①3
-213 15
+513 14
-12 15
,1 14
=(3
+513 15
)-(22 15
+113 14
),1 14
=9-4,
=5;
②14.85-1.58×8+31.2÷1.2,
=14.85-12.64+26,
=28.21;
③2.25×
+2.75÷13 5
+60%,2 3
=2.25×0.6+2.75×0.6+0.6,
=(2.25+2.75+1)×0.6,
=6×0.6,
=3.6;
④1000+999-998-997+996+995-994-993+…+104+103-102-101,
=(1000+999-998-997)+(996+995-994-993)+…+(104+103-102-101),
=4+4+…+4,
=4×(900÷4),
=900.