+=
-=
2-=
8×1.25=
( )×8=
0.25+1.5= 1.03+2.7= 16.6-12.31= 1.6×5=
+ = + = - = 3- =
20×70%= 40%+70%= 25%×40= 75%+=
0.2×2.7%= 15÷1%= 1.05﹣50%= 100×100%=
奇数+奇数=;奇数×偶数=;偶数-奇数=。