+÷+ 43×-31÷ (90+)×
++++……+
x-x=10.8 +x=20×0.5 x:=2:1.75
①99.7×13+ ×13
②12.78﹣(1.17+2.78)﹣3.83
③910÷1.3×0.7
④67× ﹣9÷1.25+ ×2
①8.02+644.75﹣4.75+2.98
②( )
③0.25×1.25×3.2
④ ×87.5%+0.125× ﹣7×