①0.78×7.2+0.78×2.8
②1.25×17×8
③5.6×4.5-4.6×4.5
④4.2×1.01
①7.4﹣6.62+20.6﹣13.38
②×+×
③(-+)÷
④2×0.8×12.5×50%
⑤÷(÷+)
⑥×[1÷(+)]