估算:⑴122÷2≈□, 378÷5≈□, 435÷7≈□, 297÷4≈□, 21÷8≈□,⑵181÷3≈□, 359÷6≈□, 440÷9≈□, 38÷7≈□, 323÷4≈□,⑶469÷8≈□, 178÷3≈□, 63÷6≈ □, 790÷2≈□, 194÷6≈□,⑷65÷7≈□, 360÷5≈□, 162÷4≈□, 410÷6≈□, 135÷2≈□,
14.8×6.3-6.3×6.5+8.3×3.718.1+(3-0.299÷0.23)×1
5.09-(0.09+1.23) 9.36-(4.36-3.5)
7.5-2.45+7.5+2.45(-)×21+
2.5×(1.92÷0.3-5.9) 24.5-(7.58+)
45.55-(6.82+15.55) 34.52-17.87-12.23