(0.5+0.5)*(0.5+0.5)÷0.5=2*是称号
(0.5 + 0.5 ) / 0.5 *( 0.5 / 0.5)=2
0.5 0.5 0.5 0.5 0.5=2 × + ÷ +
(0.5/0.5)*(0.5/0.5)/0.5=2
