(18,36)= (51,34)= (13,4)=
[15,20]= [13,39]= [7,9]=
-25%= 5×3.14= 50%×86= 12.5%÷ =
1-35%= ×18.84= 60÷30%= 3.14×32=
1.6×50= 6.3÷0.1= 1﹣= -×=