解方程 X﹣X= 2X+= 70%X+20%X=3.6.
简便运算(1)231×6.2+23.1×208﹣131×27; (2)7﹣1.125+(2.25﹣6);(3)1﹣2+3﹣4+5﹣6+7﹣8+9+97﹣98+99;(4)1++++…+.
计算3.14×67+8.2×31.4﹣90×0.31412.65÷12.5÷0.8 (32×0.63×0.95)÷(1.6×21×1.9)
解方程(1)0.4:0.3=(6﹣x):1.5; (2)2(6+x)=4x+6.
用简便方法计算.25×1.25×32(3.75+4.1+2.35)×9.8.
求未知数x ①0.36×5﹣2x=0.4 ②=.