Выполни вычисления по образцу 470 + 80 = 470 + (30 + 50) = (470 + 30) + 50 = 500 + 50 = 550 560 – 90 = 560 – (60 + 30) = (560 –

Выполни вычисления по образцу 470 + 80 = 470 + (30 + 50) = (470 + 30) + 50 = 500 + 50 = 550
560 – 90 = 560 – (60 + 30) = (560 – 60) – 30 = 500 – 30 = 470 360 + 50 = 360 + (
+
) = (360 +
) +
=
+
=

290 + 70 = 290 + (
+
) = (290 +
) +
=
+
=

830 – 80 = 830 – (
+
) = (830 –
) –
=
–
=

420 – 60 = 420 – (
+
) = (420 –
) –
=
–
=
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