(1)[9.2+0.8×(9-7.75)]÷0.4
=[9.2+0.8×1.25]÷4
=[9.2+1]÷4
=2.55
(2)3.5×9.8+0.35×2
=3.5×(9.8+0.2)
=3.5×10
=35
(3)28×
26 27
=(27+1)×
26 27
=27×
+26 27
26 27
=26+
26 27
=26
26 27
(4)[(
-2 3
)×3 5
+15 4
]÷2 3
11 12
=[
×1 15
+15 4
]÷2 3
11 12
=[
+1 4
]÷2 3
11 12
=
×11 12
12 11
=1