列竖式。309÷3=
÷[×(-)]
4.9×5+4.9+4.9×3
直接写出得数。6-+= 1-0.675= 1÷20%+0.36+0.4=÷= (+)×12= 1.25×0.9×80=+-+= 2.6×7.5+74×75%=×7÷×7= 199+200+201+202+203+204+205=
5x-12.5=2 3×(2x+7)=45 5.6-4x=3.2
(13×0.58-4.87+0.42×13- 5.13) ×4.25