估算: 127×8≈ 3×78≈ 92×6≈ 88×4≈ 6×39≈ 99×7≈ 58×2≈ 63×5≈
8-2= 6+2= 8-6=
6-3= 3+3= 7-5= 5+2=
9-4= 9-5= 4+5=
10-4= 10-6= 4+6=
5+2= 7-5= 7-2=