Wykonajmy obliczenia.

$230-50=230-30-20=180$

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$74+50=124$

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$163-50=113$

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$702+50=752$

Tabela:

$\stackrel{-50}{\to }$
$230$	$\underline{180}$
$\underline{124}$	$74$
$163$	$\underline{113}$
$\underline{752}$	$702$
$\stackrel{+50}{\leftarrow }$

$125+80=205$

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$260-80=260-60-20=200-20=180$

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$650+80=650+50+30=700+30=730$

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$1000-80=920$

Tabela:

$\stackrel{+80}{\to }$
$125$	$\underline{205}$
$\underline{180}$	$260$
$650$	$\underline{730}$
$\underline{920}$	$1000$
$\stackrel{-80}{\leftarrow }$

$642-300=342$

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$195+300=495$

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$2100-300=1800$

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$4850+300=5150$

Tabela:

$\stackrel{-300}{\to }$
$642$	$\underline{342}$
$\underline{495}$	$195$
$2100$	$\underline{1800}$
$\underline{5150}$	$4850$
$\stackrel{+300}{\leftarrow }$