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Theory: Properties of addition and subtraction (numerical expressions)

Task

Select a numeric expression equal to the expression:

\(\displaystyle (245−15)−5=\) Перетащите сюда правильный ответ

Solution

In this problem we use one of the versions of the associative law of addition:

 

 

\(\displaystyle (a−b)−с=a−(b+c)=a−b−c{\small .}\)

Therefore,

\(\displaystyle (245−15)−5=245−(15+5){\small . }\)

 

Moreover,

\(\displaystyle 245−15+5=235 =\not ​225=(245−15)−5{\small , }\)

\(\displaystyle 245+(15−5)=235 =\not ​225=(245−15)−5{\small , }\)

\(\displaystyle {\bf245−(15+5)=225=(245−15)−5}{\small , }\)

\(\displaystyle 245+(15−5)=255 =\not 225=(245−15)−5{\small . }\)

 

Answer: \(\displaystyle 245−(15+5){\small . }\)