Question

To solve: x + 3.9=4.2

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asked 2021-02-12
To solve: \(\displaystyle{x}\ +\ {3.9}={4.2}\)

Answers (1)

2021-02-13

Calculation: \(\displaystyle{x}\ +\ {3.9}={4.2}\)

Substract 3.9 on both sides, \(\displaystyle{x}\ +\ {3.9}\ -\ {3.9}={4.2}\ -\ {3.9}\)
\(\displaystyle{3.9}\ -\ {3.9}\)

Based on the definition, \(\begin{equation} \frac{\begin{array}[b]{r} +3.9\\ -\ 3.9 \end{array} }{ +0.0 } \end{equation}\)
\(\displaystyle{3.9}\ -\ {3.9}={0}\)
\(\displaystyle{4.2}\ -\ {3.9}\)

Based on the definition,

\(\begin{equation} \frac{\begin{array}[b]{r} +4.2\\ -\ 3.9 \end{array} }{ +0.3 } \end{equation}\)
\(\displaystyle{4.2}\ -\ {3.9}={0.3}\)

Substitute \(\displaystyle{3.9}\ -\ {3.9}={0}\ \text{and}\ {4.2}\ -\ {3.9}={0.3}\ \text{in}\ {x}\ +\ {3.9}\ -\ {3.9}={4.2}\ -\ {3.9}\)
\(\displaystyle{x}\ +\ {0}={0.3}\)
\(\displaystyle{x}={0.3}\)

Final solution: \(\displaystyle{x}={0.3}\)

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